Yes F2P has saved suffering P2P games from being shut down but it does usually suck a lot of the fun out of the game in the process. When a game goes F2P from P2P they have to artificially create reasons for the players to spend money. They slow down XP gains in order to encourage people to buy XP boosters, they make rare items even rarer and then add them to the cash shop to tempt you to give up ever trying to farm them, they put limits on the number of dungeons you can do in a day and then charge you if you want to run more...
The F2P model encourages the developers to implement arbitrary barriers to entry on everything that requires the player to pay for access. If you then compare the cost of full access to the game for a month under the F2P model it's typically many many times higher than a regular monthly subscription which would grant the same full access under the P2P model. This happens because statistically only about 5-10% of the players ever decide to pay under the F2P model (the rest usually struggle under the restrictions before getting bored/frustrated and quitting giving F2P MMOs a much much higher player turnover) so those few that do pay have to be milked for all they're worth.
I have never seen a P2P MMO transition to F2P in a way that didn't cause the game to become far more grindy (to encourage cash shop purchases) or cost more per month for the same access. It just doesn't work. From what I understand of SWTOR now it's a relatively fun SRPG up to the level cap and then suddenly you have to cough up a small fortune to do anything at all at endgame. From a business standpoint it can be considered a success because there are a lot of rich players out there that are happy to sit on top by spending $100 a month (yes this has happened in countless F2P games) but from a gameplay standpoint if you have to be rich to have fun then it's not a good game. Just because something is financially successful does not make it good; Twilight and Justin Bieber are good examples of that.
As I said in another post, the F2P model can work in a game that was built from the ground up with that model in mind. The gameplay systems can be shaped around it so as to be less restrictive on free players whilst encouraging spending of money in a way that doesn't feel coercive. For a P2P game though, introducing the F2P mechanics has never worked out favourably for the players in any game I've ever seen make that transition.