If sprint still babies iDen after this many years, it's ridiculous to think sprint will dark wimax anytime soon.
I say it's wimax lights out in 2014 or early 2015. That's plenty of time to get your LTE upgrades in.
If you chose to be a holdout because of some romantic attachment to wimax, enjoy being 3g only.
"I have the bestest, awesomest ROM ever, only my camera, GPS and Bluetooth don't work"