Trying to future proof is one thing, and trying to go with the best carrier/hardware is another.
I'm pretty solidly committed to VZW right now (I currently own an envy2), and I've been following the Moto Driod and HTC Eris with interest. At this point I'm thinking I will wait for whatever HTC Nexus One equivalent phone shows up on Verizon whether it's called the Dragon, Bravo, Passion, Incredible, or whatever... However, looking at
Pliablemoose's thread here causes some concern:
http://forums.anandtech.com/showthread.php?t=2035864
My concern is specifically with the statement made in the article regarding carrier differentiation attempts resulting in custom UI versions of Andriod, and this leading to delays in releasing the latest versions of the OS for some hardware manufacturers. Looking at Verizon, the HTC Eris is on Android 1.5 and the Moto Droid is on Android 2.0. Rumor has it that the Eris will get upgraded to 2.0 eventually/soon, but the delay compared to the Droid should be taken into account when considering which brand manufacturer to go with IMO.
I'm also siding with the idea that Google is not going to be putting out their own unlocked phone. If you look at Google as a business, it really doesn't make much sense for them to enter the cell hardware market. They would HAVE to support end user customers, which is something they really don't like doing (because it's expensive).
Given that, you'll be stuck relying on whatever hardware/carrier you have to support and update your Android phone. So, you really want to make sure you get the hardware manufacturer that will stay up to date with Google's latest version of Android as closely as possible, and a carrier with a good app store since it looks like the app stores will be carrier specific.
Honestly, right now, as a consumer I'm a little overwhelmed by the Android thing and I'm waiting at least until the new HTC Android 2.1 phones come out. First if all, I'm interested in these phones. Second, it will be interesting to see if the Moto Droid gets Android 2.1 before or after the HTC phones.