In my (informed) opinion, if a Google + Dish network goes forward, it will be exclusively LTE. No other standards are certified for that band class (AWS-4 in this case, plus whatever else Echostar picks up), and the other data-focused/data-only standards (EvDO, DC-HSPA+) don't measure up in terms of bits per Hz capacity.
So, think Clearwire, but with better spectrum, FD-LTE (a 20x20 nationwide channel, like Verizon has done in 700MHz except with less coverage and double the spectral capacity) and more Google involvement. I wouldn't be surprised if this spectrum got hosted on Sprint's NV architecture for a rapid deployment, though mobile coverage would be limited to bigger cities for awhile, because:
1) Mobile coverage on AWS-4 will be a noticeable bit less, all else equal, than PCS, though
2) if you're covering an urban area your PCS sites are spaced for capacity rather than coverage anyway, so you can drop in AWS-4 equipment and still have a full-coverage network
I'll be the contrarian here and say that AWS-4 alone IS enough spectrum to deploy a nationwide network, or at least an urban-focused every-part-of-the-US one. 20MHz FD-LTE is nothing to sneeze at, and the spectrum is high enough frequency that network capacity issues will be slower to come than, say, VZW or AT&T's 700MHz deployments (t the expense of reduced coverage per site). Plus, if Google+Dish has capacity issues, Clearwire is just a phone call away