Right on. I'm totally with you, and I'm building based on the same assumptions. I will go to the MMM and a 6s when they come out, but don't want to have a temporary motor. That's why I got the 1940/10 hi amp. It's a lower KV (1500) and will deal very well with the higher voltage later. You might try BrianG's motor calculator too. Very helpful. Here's a link for it:
http://www.scriptasylum.com/rc_speed/index.html
Welcome to the forum!