What would be nice is being able to use the L and R buttons as extra item buttons.
For example;
Select = Bicycle
L = Super Rod
R = Itemfinder
Also, I don't think there will be that many changes, as I'm guessing that FR/LG will be using the same game engine as R/S. So I'm not expecting day/night for instance . (hope I'm wrong about all that though. :) )
Going to Jhoto would be nice - perhaps it will be a cut down version, like in G/S/C where you got to visit a simplified Kanto.
Otherwise, I expect to see a lot of the pok?mon missing from R/S, (making trading essential between the two versions), perhaps an extended safari Zone (although maybe that would be too dull?)?
Expect to see Contests, Dive Spots, and hidden islands here too.
I reckon the Unown will appear too, even if they don't include Jhoto (because trying to get all variations from colluseum, or the mythical remakes of G/S/C)
the end.
;)