I wouldnt class my self as any fanboy personally. Considering at one point i was ready to leave and join AoC while i was Beta testing it.
It's more to do with the fact that there is NO other mmo with as much polish, stability and enjoyment factor on the market today to beat WoW.
I have so much faith in Blizzard for making amazing games, that this will be the case when WotLK launches and even then it'll be hard to come close to the enjoyment of WoW.
The only game that will make any kind of impact on its playerbase will be another game made by Blizzard.
So if I'm a fanboy of anything, it would be over Blizzard and personally i don't feel like that should be considered a bad thing in anyway.
Hmm that is YOUR personnal opinion imo. Did you play mmos like Uo or DAOC? I really would not say that those games did not have as much polish or stability. These two games are the best mmos hand down i ever played.
Wow is only sucessfull because it was the last (real) mmo released in the past few years and that it had a lot of hype around it, being made by Blizzard(that i really like i must say), when UO was released there weren't enough player for it to get as much as an impact. But still this game had the best ideas i have ever seen in a mmo.
I played wow in beta, and at start(think i must have been one of the first from Switzerland to log in and create a char, that was at like 3am when they first opened the server). I got rapidly bored because, for me at least, wow is really linear, you just do quests till max level, then either raid the same old dungeons or pvp. I find wow pvp really bad and i've always been a pvper(in UO PK, anti-PK and in DAOC well... RvR was a blast in fixed teams) so it was a major let down, then they introduced the arenas, i though that was a nice idea, until i noticed it just became a "Hope the team you are going to face is not a combo you can't beat AND that they have not better gear than you or you are going to lose". I will not even speak about BGs, that is just boring, more comparable to a CS game than to an actual MMO.
I don't think WotLK will change anything, the same players that are on WoW at the moment will continue their grind to get 10 more levels and then the raid/pvp loop will settle back in place. But this time players will have more choice to make than just choose between Wow and no MMO.
I think you are a bit too confident that WoW will never die, EVERY mmo EVER made always ended by losing its population, that is a fact, UO EQ1 DAOC etc.. for all of them it was the same scenario. Saying that Wow will only lose people when Blizzard releases another game is really optimistic, they are not god on earth, sure they make really good games but i doubt they are the only company able to release a good mmo.
Well you can be a Blizzard fanboy all you want, but then let me be a WAR fanboy will you ?

I guess i must have as much faith in Mythic than you do in Blizzard, the only difference is that Mythic are on their second MMO and maybe that gives them a bit of a headstart. Also don't forget that most MMO players at the moment seems to want PvE because that is all Wow offers properly, i for one prefer Pvp in an mmo and i can't wait to try War!
Sorry for the lengthy post but i'm bored at work hehe!