Probably not for a while...
It's fair to say the 5 will be ligher and more efficient but where does everyone see the tablet market progressing to in the next few years?
What are long term changes you'd like to see in the iPad?
Interesting question. All signs point to an evolutionary progression the things we'd all assume: thinner, lighter, faster, more battery life, better wifi, an even higher build quality (i.e. tougher gorilla glass).
The wild cards are going to be, I think, ways in which the device gains ever more nuanced sensory input and feedback. Wacom tech is an obvious one. Figuring out a way to combine the benefits of LCD and eink is one. 3D gestures will be a big one, just look at Leap Motion for that.
This is a software driven industry now though. A trend I see is more and more reliance on gesture instead of GUI. This is great. Gestures are the keyboard shortcuts of touchscreens.
Another thought in terms of sensory input: I think home automation is going to be a big thing. Look at the Nest thermostat, Philips smart bulbs, wemo by Belkin, etc. Convalescence around your tablet or phone will be a boon to the home automation industry.
I think with increased bandwidth due to 4K video being mainstream, among other things, perhaps a feature like Siri listening to everything you do can be afforded, and Siri could spontaneously interject conversations with suggestions or insightful comments, or respond to questions without being invoked by the home button. I know that sounds kind of creepy now, but it'd be an option and I think people would support that idea by then.
I do think there will be an even bigger "ipad" that runs a special build of OSX; or a special build of ios. There would be real benefits to all kinds of people if they essentially had a small Cintiq to go.
I think all or most of this will happen eventually, but apple won't do it until they can do it right, and the market is right, etc.