From Engadget:

"I am an engineer with Sprint and can tell you that the WiMax build out has not stopped or slowed. The joint venture deal with Clearwire is the only thing that faded out. There are to many contracts in place with various equipment vendors (Nokia and Samsung most notably) to just scrap the entire project."

http://tinyurl.com/36knfm

No way to confirm who this person is, but who would claim to be an engineer with Sprint if they were not?