Maemo 6 most probally. Symbian^3 seems to get pretty much all the stuff that Symbian 9.5 was supposed to be, starting from screenplay, but nothing like Symbian^4 where Maemo 6 should be compared.

AVKON will be pushed away for Qt in Symbian^4 and we should be seeing Nokia's direct UI. It will be totally different beast compared to Symbian^3. My guess is that it's UI is similar to Maemo 6.

Considering Maemo seems to be targeted for people like me i would be going for Maemo 6 when it comes rather than Symbian^4, but you never know.