I really don't think Rift has gone out of it's way to compete with WoW, more like it has tried to give players who are bored of WoW something slightly different to play.
Sure the leveling is very similar, some of the PVP is similar, dungeons are similar, but they have given players lots of options to do things differently.
Whether it will live for years and years, who know, I doubt another MMO will live like WoW has now, WoW is now Activision Blizzards cash cow, hence why it is being toned down to cater to everyone. The future lies in games such as DCUO, Rift, GW2 and SW:TOR for gamers bored with WoW.