It would be pretty irrelevant now. The GC one might be worth picking up, I played that after Wild World and enjoyed it, but honestly all of them will be so mechanically inferior to New Leaf.
I enjoyed the Gamecube one a lot which was why I was always reluctant to buy the DS one because I was worried it would be too similar. I guess the only thing I'd really be missing was Gen 2 music and some increased museum features.
Also, how do I share my friendcode so that I can play with some of you when the game comes out? Do I just post it here and wait?