Judging by the glacial progress iPads have made, I think they'll be exactly the same as they are now, except thinner and lighter. I'm sure they'll still just be large phones that can't make calls, last 8-10 hours on a charge, have no multitasking, have no speaker layout that makes any sense...
Maybe Apple will manage to properly implement external keyboard support by then, though that's probably a pipe-dream.
Windows 10 looks like a step back from 8.1 even, and I didn't even think 8.1 was any good. Android also looks just as bad as in 2012 (on tablets, much different story on phones), so I wouldn't hold my breath there either.
I don't know what the future will hold, but I'm past certain that it will revolve around the laptop / netbook form factor.
Then again, I'm an idiot. When the iPhone was first shown, I was certain it wouldn't catch on, and when the iPad was show, even more so.