2 things:
1)every game will get old after a while.(that's why every(most ??) MMO have expansions and content patches, the most brilliant idea will become old and dull given enough time
2)GW2 will have no subscription fee, so you can leave and ge…
eve online have no instancing
and i have been in battles with ~3000 player (about 1500 vs 1500) (it was unplayble but they are working on making it possible and playble )