Articles have re-emerged over the past few days about the possibility of Apple releasing a larger iPad, primarily intended for educational applications (or possibly other cases where what is required is a "semi laptop" replacement). The rumour was apparently started in May 2013 by this web site claiming that Apple was to release a so-called "iPad Maxi".
So far, Apple has stood out from other manufacturers in limiting the number of form factors that iOS apps must cope with, much to the delight of developers. (This situation contrasts with Android, where it is almost impossible to test apps with all available form factors, leading to occasional incompatibilities with some applications on certain devices.) The most major change of form factors so far for developers was from the iPhone 4 to iPhone 5, involving a change in screen resolution in addition to a change in physical size. More conveniently for developers, the change from the classic iPad to iPad mini did not involve a change in resolution (bearing in mind that to the developer, supporting retina vs non-retina usually involves at worst minimal code changes). The iPad's "retina" resolution could presumably be scaled up to a 13 inch screen without affecting quality too much so it would be interesting to see if that is the way Apple would go, or if they would feel compelled to increase the screen resolution despite the burden for developers.
But I wonder how much of a market there is for a larger iPad as such. A strength of the iPad is its portable, lightweight design and the recent focus of its development has been on miniaturisation. There are definitely cases (software development is a case in point!) where the screen size of the iPad is a limiting factor. However such applications tend to go hand in hand with needing the facilities of a "full" laptop and for a "semi lightweight" solution, Apple already offers the Mac Air range. With the introduction of iCloud integration, the company appeared to be making efforts to establish the tablet vs the laptop as their main way of differentiating form factors (remember the adage that the laptop is "just another device"?). It seems to me that if another size of iPad was introduced, it would be backtracking a little on this philosophy.
Time will tell how much veracity there is behind the iPad Maxi rumour...