Umm... WiMax is still years away from deployment, and even then, it will be in few, select areas. The best thing to do will be for them to implement EVDO Rev. 0 fully, then Rev. A, Rev. B, and so on. Rev. B and Rev. C have already been discussed. Curious, why do you see WiMax as the future? The CDMA networks will always be that, a CDMA network. The only thing they might use WiMax for is data as of right now, but CDMA is a superb network and does not need to be replaced anytime soon.
I ask again, why WiMax? It is extremely expensive to roll out right now, so it will be a few uears before it is even put up.
Really? Sprint is investing $1Billion in 2007 and up to $2Billion in 2008 to roll out WiMax:
http://www2.sprint.com/mr/news_dtl.do?id=12960
It's already scheduled to be available in trial markets by the end of this year... that's a far cry from it being years away.
Eventually, technology like WiMax could replace CDMA/GSM/etc by using it the same way you'd use Vonage or Skype... VoIP.