Agreed.
I don't think the Nexus and the SIII will be so different to warrant use of another upgrade. I chose the Nexus because it has everything and more than what I need and it also has developer support for what I predict will be at least 2.5yrs. This phone is indeed developer friendly (not to say the SIII won't be), but this is as close to the OG Droid as Verizon has had. Sure it's not as popular (as we have more options now compared to back then when the Eris was the only "competition"), but I'm sure it will have the same support. Developers have since only improved and the quality of ROMs now are going to be much better imo.
The SIII will be a solid phone I'm sure, but nothing can pry my fingers off my Nexus unless it's the Nexus 2, which better not come out in 2012.