If there was no more PC version I do think the playerbase would take a massive hit and would likely no longer be sustainable at the current development schedule, which would likely cause a significant portion of the console player base to stop playing as well. Now, would it actually die? No. I mean, FF11 is still going after all. Once you have an established MMO you can basically just keep it in maintenance mode for perpetuity with possibly the occasional small update. It won't pull in any new players, but the ones who just can't live without it will stick around.

As for the PC side of things, which is where I play, I don't really care about add-ons at all. I don't use any of them and don't care if others do as long as it doesn't impact my personal experience of the game, and I see little chance that it will given I don't do the hardcore stuff in the game anyway.