Just a personal anecdote: the upgrade is happening for me. I got an upgrade available notification and upgraded to ICS yesterday. It's on an HTC Incredible S, for which HTC announced the update a while ago but with no firm date. And the update arrived out of the blue for me, I wasn't expecting it now (there were rumors for Q3). My phone is not subsidized by the way, so expect more delay for operator controlled phones.
So it seems to happen, if slowly. I think it's important for handset makers to generate a positive customer perception. If HTC hadn't bothered to upgrade my phone to ICS, I would have looked elsewhere next time (Nexus most likely). As it is, I'll consider them again.