If Sprint says nothing, there will be 3 weeks of daily media speculation over whether it's an iPhone or a dual-core Android phone. If they say one or the other, half the buzz will instantly vanish.
I seriously doubt it will be an iPhone, though. The bigger sparks flying will be if Sprint DOES get to have the iPhone5 along with AT&T, Verizon, and T-Mobile this summer, but gets told by Steve Jobs that wimax is NOT an allowed option. Especially if Verizon's iPhone 5 is allowed to have LTE. Personally, if Steve did that, I think Sprint would make a very, very big deal of publicly telling Steve & Apple to go self-replicate themselves.
I don't think that even Steve Jobs would be *that* insane, though. Given how crazy some people get about the iPhone, if Steve refused to let Sprint have wimax and refused to allow T-Mobile to have HSPA+ (but allowed VZ and AT&T to have LTE, on different bands no less), he'd probably find himself spending his September testifying before an angry Senate subcommittee demanding to know why (off the record) their (grandkids|staffers|*) are screaming at them and crying...