The good news in this case is that if i've done the math right, by this point the amount i've saved going with T-Mobile's non-subscription plan has more than made up for difference from getting an unlocked Nexus One rather than a subsidized one. The first downside is that it seems pretty certain at this point that the new Nexus is going to have pure software buttons. I think the semi-software buttons on the Nexus One were a mistake (they have caused persistent problems for me) and this is totally a step in the "wrong wrong, absolutely brimming over with wrongability" direction. Soft or semi-soft buttons are too easy to accidentally hit while trying to do other stuff, and that's without the occasional problem where the screen goes wonky and thinks you're touching it offset from where you actually are (both my Nexus One and shelleycat's Droid demonstrate this behaviour from time to time) or locks up and refuses to recognize touches to the main screen at all. And overall i really want a few extra hardware buttons to allow me to manipulate the phone without turning the screen on at all. I do this all the time with the volume rocker, but i also want "pause", "play", "forward" and "back" buttons as well to use while listening to music or audiobooks.
The other big problem is it's not certain which carriers are going to get the phone. The most current rumor i've heard is that Verizon is going to have temporary exclusivity for the first couple months. I've been very happy with T-Mobile, but they may or may not get absorbed into AT&T, depending on how the various FTC inquiries and court cases go. I liked the theory of having a GSM phone that i could use in other countries, even though that never actually happened in practice, but i'm not too fond of AT&T. I'm not especially fond of Verizon either, though they'd still be better than AT&T, despite the GSM/CDMA thing. Sprint was my old company and i was kind of meh about them. Their online interface sucked when i left them in... early 2010 i guess (somehow it seems longer.) I had multiple issues with trying to get my account re-registered when i got a new phone after my ancient one got busted, which doesn't seem like it ought to have been a problem for them. I switched to T-Mobile because they were cheaper, but they've also seemed more competent and friendly than Sprint ever was.
So i'd love to stick with T-Mobile if the merger isn't actually going to go through, but if i get a new phone with T-Mobile now and the merger does happen i'd have to either ditch the phone or live with AT&T. Otherwise i've got to decided between Verizon and Sprint (since it seems unlikely MetroPCS or anything like that is going to get any of the really cool new Ice Cream Sandwich phones.) In that sense maybe it would be good if Verizon gets some exclusivity on the front end. It wouldn't kill me to stick with my Nexus One for a few more months, and maybe by that point the situation with T-Mobile and AT&T will be a little more clear.