I really hope Masa knows this. They have the capability to deploy the second carrier and have for a few months now. In my humble opinion this should have priority over B26 & B41 integration due to the vast majority of sprint subscribers with B25 only devices. You can't have sub 1mbps speeds on a "brand new 4G LTE network" in completely built out markets. And even in partially completed markets a second carrier would do wonders to alleviate the uneven load on towers AS WELL AS overall capacity issues across the board.
Looking forward to the next few years, mobile data consumption will increase at an exponential rate while adoption of tri-band capable devices will only increase at a slow, steady rate. Unless of course Sprint decides to give everyone free, no strings attached tri-band capable phones which is about as likely as big red and the death star offering unlimited data again.
Edit: If you ask me, Sprint should just slap on 2 additional B25 carriers where they have the spectrum. In 3 years, two 5x5 carriers will likely be just as constrained as the single carrier is in some markets today.