Though the rumor of a bigger, around 13in iPad has been alive for a while, it has picked up some traction in the recent weeks . As usual iMore has a great article on logistics of the screen size and the pixel density of this rumored iPad Pro . There have been a lot of arguments and discussions in the past of whether an iPad is a predominantly a consumption device or if it can be used for creation as well and Apple has been trying to promote the iPad as content creation device, a little more aggressively, in the last few weeks . While I agree there is a great potential for the iPad to be a content creation and a high productivity device, it cannot replace a traditional computer for the most of us. Although, I need to mention that there are a lot of prominent people who do a lot of work with words and photos who use the iPad as their primary computer, like Andy Ihnatko of the Chicago Sun Times . But this article is purely from my experience of using an iPad (a mini in this case) for the past year or so.
I use the iPad mini for reading, playing games like Asphalt 8, watching videos, browsing, using Facebook and Twitter. For all this it works great. It is the perfect weight and size for a one handed use. Its lack of retina display (I have a first generation mini) has been recently solved by Apple  and it seems to have rave reviews . One more thing I use my iPad mini is for note taking and annotating pdfs and from my experience it works flawlessly  and probably better than the full sized iPad, though the new iPad Air  might change my mind in this aspect.
But what is preventing me from using the iPad instead of my MacBook Pro, full time? The one thing that comes to my mind is multi-tasking. Apple has made significant strides in this aspect from early iOS versions to the the most recent iOS 7 release. However the iPad has always been designed to be a one App at a time device and I am sure that was what was envisioned by its founders as its best use case. This is not a bad thing in any way, except when you think of a more expensive iPad! As of now the iPad is priced right, starting at around $499 for the lowest iPad Air version and $399 for the mini. That is roughly half the price of the cheapest 11in MacBook Air, at round $999. So according to Apple (purely from their pricing, not officially), an iPad is supposed to be a companion device than a stand alone computer. Again as per what it was intended for, the iPad has not just lived up to its expectations, but has out performed by miles. It is by far the best tablet computer to have ever been released and is continuing its stride, with no (sales) saturation of any sort in sight .
But... yeah there is always a "but"... for my use case of a computer (I consider myself an above average user in terms of my computer usage intensity), I just cannot replace my laptop with an iPad as of now. I need a better multitasking interface where I can quickly swap between Apps, sometimes see them side by side at the same time, exchange the same data across different Apps, etc. All this is simply either not possible or too much time consuming to do on an iPad. Also remember that all the Apps in iOS are sandboxed, in the sense you cannot use data from one App in another freely. This leads to a lot of duplication and utter confusion. This is on top of woes like not finding the exact replacements for the programs I use on my laptop, like Matlab for example, for iOS, even though the iPad specific Apps in the App store run in tens of thousands in number.
Where am I going with this is that, for justifying a need for a bigger and/or more powerful iPad, I need to be able to do much more with it than what I do with my iPad currently. As of now assuming Apple releases the rumored iPad Pro sometime in the next year, it is fair to assume that it will be priced between the current iPad and the 11in Macbook Air. Is a bigger screen (and probably beefier internals) enough to justify this price? I don't think so.
Microsoft has its flaws and quite a few of them actually, but are approaching this post PC era with a vastly different approach from Apple's. Apple has built a dumbed down and a simplistic version of a solid full fledged Mac OS and has called it iOS. Over the past seven years, iOS has been improved drastically, making it a more capable mobile OS than ever before. In theory the ultimate goal, iOS is aspiring to reach, is to be emulate Mac OS X in terms of capability. Now consider Microsoft's approach here, they just force bred a mobile OS and the classic Windows to an unimaginative Windows 8! The infamous toaster-refrigerator offspring  is neither innovative nor good looking nor efficient and is certainly not selling well . But there is definitely something important to note from Microsoft approach, they are also trying to reach a post PC OS that is as capable as their classical desktop OS, to be used on post PC hardware, like a tablet.
Even Samsung with their famous Galaxy Note has a boatload of features like, two Apps at the same time in either half of the screen, extensive stylii support and many more features. Of course Samsung's approach to anything has been throwing Spaghetti at the wall and seeing what sticks (and copying Apple ). Samsung has not got any of this right yet and its approach is not even close to being successful in tablets, as except for a niche market share, Samsung has been struggling to compete against Apple in the higher end tablet (and smartphone) market , . It is nevertheless another approach to this conundrum of pushing post PC OS to match the capabilities of the classic desktop OS without sacrificing the inherent advantages of the post PC hardware, like portability and battery life.
Assuming there is not going to be another OS from Apple, other than Mac OS and iOS (some have even suggested that these two OSs might merge into one, that would resemble iOS more closely that the Mac OS) and I am fairly certain that there isn't going to be one, we are left with iOS for the iPad. iOS 7 is extremely capable and all the internals of the iPhones and the iPads are overpowered according to many . This means only one thing, the statement Apple made, calling the iPhone 5S the most forward thinking iPhone ever, should indeed be true. As of now I think they are only scratching the surface in terms of capabilities of both the iOS and the iDevices. In my mind there is no doubt that if Apple can deliver the same flawless performance that Mac OS offers on Apple computers, on the iPad, they would deploy all the capabilities and feature sets of Mac OS in iOS, right now. But iOS is not yet there. Hence in conclusion, if we see an iPad Pro released next year, I would predict that we will also see a much more powerful evolution/version of iOS (in terms of it metamorphing into more like its Mac OS counterpart) emerge in conjunction with the mighty rumored iPad Pro.