I would never, ever play a microtransaction game. I've been playing since my 7x GM tankmage in UO, 50 druid in EQ1, Doctor/Bounty Hunter in SWG (pre NGE), and current 75 mage in WoW. Along the way I've tried EQ2, Asheron's Call, AC2, AO, AoC, Vanguard, and LOTRO. I've never had a character deleted. I've come back 1, 2, 3 years later either paid or during free come back promotions and my characters have always been there.
I would never play a game with ads in it either.
Want your MMORPG to succeed? Fix the bugs. Don't let overpowered classes/specs/builds run rampant for too long (i.e. crossbows, tamers in UO, combat medics in SWG, rogues in WoW). Make new content. Set up a decent grind.
The subscription model is in no danger of dying.