I was around when Sprint bought Nextel. The Sprint fanboys were in the same utopia as they are now. They thought they were going to rule the wireless world with the best coverage, best PTT offering, best phones, best speeds and highest ARPU. They were going to destroy Verizon and dominate the US wireless market.
2.5 GHz networks have great capacity capabilities but the range is abysmal. With best efforts building out new sub 1 GHz networks and PCS networks from scratch are poor and spotty at best. 2.5 GHz will be even worse. I doubt Son is dumb enough to pour in the capital to build out 2.5 GHz to the extent needed to be ubiquitous and will instead only use it in the most dense urban markets where the highest needs are.
Facts are that Softbank, as successful as they were in Japan, are not guaranteed to replicate this success State-side. By many accounts even in Japan their service "sucks." The United States is a market unlike no other on earth and the challenges to build out far exceed anything SoftBank has ever had to encounter. The incumbents will not make it easy for them either.
A large part of Softbank's Japanese success was in part to being an exclusive provider of the iPhone. Here the carriers compete by having the best phones exclusive to themselves or pricing themselves down down down. Son doesn't want to allow the competitors to capitalize on growing data revenues while he offers unlimited data with capped fees.
I'm trying to find the interview he made with a reporter where he claimed he would have to continue to offer "unlimited data," as long as Sprint's network was poor in comparison to their competitors.