Every MMO that has gone FTP ends up in the dust bin for me, the exception being EverQuest though I am still playing a SUB for that (it just doesn't require one to play at the lowest level). Inevitably major sections of the game ends up being part of the in game store. So much so that to play what I feel should be the standard base game tends to cost _way_ more than a SUB would. They introduce boring and annoying grindy mechanics that you can speed this one tie _if_ you pay a small fee. It just adds up to a unfun experience.
People like to cite GW2 as a good example of FTP games out there, which manages to get new content out every 2 weeks. Which is good, though I wonder how much of that is really being paid for by the one time purchase of the game vs the in game store. If its the former than expect a _heavy_ push of the store, possibly imposed pay gates etc, when that money dries up. Or they could begin to jam most of the content updates into xpacs.
As for ESO. I'm still not convinced of the games concept to begin with let alone whether it deserves a SUB.