Doesn't look like it. They just came out to Sprint in October.
But, used prices are starting to slip a bit. You might be able to pickup a used Sprint iPhone 4 for $350 to $400 and a Sprint iPhone 4S for a bit more. You'll have to use eBay or Craigslist.
If you go that route, the only way I'd do it is to use Craigslist, buy local, and meet seller at a Sprint store, activate line/phone, then pay seller. Too many hot phones out there.