imo I would like them to aproach the map in a oblivionish type way (hold flaming)
A huge world, but with more emphasis on each city. Make them huge and making the innards of the city look less generic. More backalleys between buildings, just heaps of subtle features like that. I think the size of the country side of SA was perfect. And perhaps have hidden surprises all throughout the country side such as little houses or (maybe a little too RPGish) but caves that could be used as a hideout etc.
And last of all upgrading the graphics. I know some people complain that it will loose it's trademark arcadish style but if the game resembles some of the fake images i've seen then it would be a definate asset.
Well thats my two cents.