I have no idea how good the developer network will be on the OneV but I plan on getting one for my mom. I'm not sure if the OneV will be rooted, I have to see how it works for her first, and even then I won't be able to do a lot of dev work on it.
Personally, I will be getting the 3D on launch day (or before), as for what I will make for it... Hard to say, it has a lot of options, GB, GB with Sense, ICS or ICS with Sense. One way or another it will get a version of Harmonia unless HTC/Virgin lock it down incredibly well, but I'm not expecting them to.
The 3d already has a good dev community and they already started tearing apart the Virgin rom for it, so if you are a flashaholic, that will be the phone you want. I have no idea how many other devs are upgrading and I don't know to which phone.