There's an interesting article about this trend on IGN right now. They interview the CEO of Wargaming (World of Tanks), who makes the comment that for FTP to work, the game really has to be designed from the inception with that in mind, and so subscription games that convert to FTP rarely work.
Basically, the steps in the article are:
1) Make a PVP MMO wargame with a cash shop
2) Market it in Asia
I get what the article is saying about creating a game as F2P, rather than adding that option later, but in that case, GW or GW2 would be a better game to compare SWTOR to than WoT. It would have been interesting to see what SWTOR would have looked like if it was planned as F2P.
Also, I'm not sure that converting to hybrid system "rarely works". For example, LOTRO and DCUO are still coming out with new content, in spite of the stigma that going F2P has.
What hurts MMORPGs more than anything is the fact that there are so many out there and people have limited time to play and money to spend. Add to that that when a new MMORPG launches, the people who play the new game are largely drawn from the populations of other games, rather than from people who don't play MMORPGs. Granted, not everyone is drawn to the same genres of gaming, but essentially there's a finite pool of players with a limited amount of time and money (well, unless you open up to new markets, which takes a lot of money to do).
Honestly, though, that being the case, going F2P is a good way to draw people back after they've gotten tired of the new game.