Adding a GPU seems logical, as does a resolution change.
Higher than current resolution on a 27" or thereabouts panel is incredibly expensive, and will be so for YEARS to come. Nobody in their right mind are going to pay 5k+ for a computer monitor except for those few who are so rich that money is of no concern to them.
Adding GPUs to the TB display would also be a fairly poor move, as external GPUs that are significantly faster than those typically built into a notebook-class computer cost quite a bit of money. Remember, even the 2012 MBA will get a significant upgrade with Ivy Bridge graphics (40-60% or thereabouts.)
Also, discrete graphics chips draw fairly hefty amounts of power (midrange devices suck down around 100 watts or more), thus neccessitating more cooling and a bigger power supply, increasing heat output and possibly noise, and adding further costs.
The final nail in the coffin is lifespan. GPUs age quite rapidly, performance-wise. Performance of a graphics card more than 3 years old is usually bad, or very bad compared to anything current, even budget cards. Only the most expensive cards can still compare to even midrange offerings after a few years.
Most expect to hang on to a monitor for a lot longer than that. And if anyone's thinking about upgradeability; HAH! This is Apple we're talking about, remember? You can't even upgrade the graphics in an iMac, and they would do it in a monitor? Just knock any such ideas out of your head, please.
Of course they'll get thinner.
Not really any reason to make it thinner. It's a monitor; it just sits there on your desk... Making it thinner would just complicate the design of the innards. Remember, there's speakers and stuff in there as well, and that has to fit somehow.
Connect without having to physically connect is another possibility, ditch all but the power cable.
High-bandwidth wireless communications is unfeasible. There's some systems out there for video mainly, but they're glitchy, very short range and expensive.
Nothing will come out for years that can match even current-gen thunderbolt, and it might well never happen. Wireless tech is inherently a lot less reliable than physical cables.
No, I wouldn't expect anything revolutionary to the next generation of TB Displays. USB3 will likely be in there, considering it's being included in next-gen Macbooks (and I assume, iMacs.) Possibly they'll do a higher color gamut backlight or something simple like that, but I wouldn't count on it. The TBD is already an expensive piece of kit, so most anything else they can do would push the device into "super expensive" price range.
