Lets see here... ARM7 and ARM9 aren't backwards compatible, so they can't update the second processor to an ARM9, or replace them both by an ARM9 dual-core, which means they can't add a second touch-screen to it (not that that would be forward-compatible, so I don't think it would happen).
Getting rid of the GBA port won't happen - do you really think they will cripple Pokemon? 
I suppose they could upgrade internal memory to be able to hold more from DS Download + Play.
They could upgrade to 802.11n, but that seems unnecessary for the DS at this time.
I suppose a firmware revision that enables a web browser, Mii Support, possibly increased Wii-ness (channels, Wii store, etc) would be possible....
Please, PLEASE do NOT feed the trolls.
fksumot tag: "Sheik had to become a man to be useful. Or less useful. Might depend if you're bi."
--Predictions--
1) WiiFit will outsell the pokemans.
Current Status: 2009.01.10 70k till PKMN Yellow (Passed: Emerald, Crystal, FR/LG)
