F2P might've been too expensive to implement considering how long they've labored as a traditional model. Probably have been in the red the whole time.
I'm surprised the producer didn't go into detail on this (the financials) more in that swan song letter. I would think Warhammer has enough of a fan base to keep this game solvent on a F2P model. Especially seeing everyone here mention how they were waiting on it to go free. I'm sure a lot more had the same idea. Hell, I'm waiting for FFXIV to go free (and I'll probably do the same with Elder Scrolls) - I'd love to play them, I just don't want to pay a monthly fee for an MMO when the market is awesomely saturated with so many great games.
On a side note - Is DAoC still on a pay to play monthly fee? The website doesn't seem to give details. There cant be THAT many people still playing it and I don't see EA pulling its plug.