Roller skates would be cool, but its even harder, especially in 3d roller skating through and on grass, bothe route and wild pokemon grass. It just... Doesn't seem right. Biking maybe would work better.
And on the subject of the person who said that the bike animations would not look good in 3d, you may argue that as well with the walking turns, and also, there is room for them to look way better in 3d, but I guess it depends on what game freak decided.
At any rate, they will probably confirm or deny this at some point in the bearish future so I guess we'll wait and see what happens.