http://kotaku.com/5540446/nintendo-3ds-going-widescreenDespite what Kotaku says, this looks like a development board (rather than a test bed - compare to the GBA development board
http://shiggsy.gbadev.org/unit.php?unit=10), so I would say that the top 16:9 and bottom 4:3 screens are here to stay.
Here's a list of specs that I am guessing at:
Same button count as DS (and all digital) except for an analogue nub (similar to PSP) and possibly additional analogue sholder buttons
Stereo speakers
Top touch screen as well this time (I believe I can see a control cable leading to a touch overlay)
Support for DS cartridges
Wi-Fi but no bluetooth
Initially available in at least white (educated guess here based on the analogue nub)
Again, all guesses! It will be interesting to see how Nintendo squishes all those buttons in with an analogue nub and prevents overcrowding. I'm guessing the reason for the analogue nub is because this will (again) be a system that fold in half (surprise, surprise!) and anything else would get in the way.