Five bands? Realistically, that would be too many bands for Sprint to juggle. Not to mention, all devices would be highly proprietary to Sprint -- any chance of using unlocked devices would go out the window.
I really do not understand this mentality that Sprint should gobble up any and all spectrum that it can. That mindset reminds me people who have faced famine or poverty, then hoard food or money to the point of irrationality. Have you really felt that starved by Sprint's prior network woes?
More and more, T-Mobile's network modernization strategy is looking better because of its standardized simplicity. It focuses on only two bands, PCS 1900 MHz and AWS 2100+1700 MHz, both of which are firmly established. The downsides are that T-Mobile's spectrum holdings are too variable from market to market and include no sub 1 GHz spectrum. Sprint already trumps T-Mobile in those two regards.
AJ