T-Mobile USA’s five-year plan is nearing its end point, as it was put into action in 2018, and CEO Mike Sievert is already giving indications of what may be including in the next plan. The third US MNO, in the past four years, has changed from being largely a low-cost operator targeting the lower rungs of mobile subscribers, to a disruptive marketing force that has gained significant market share through its aggressive pricing and content offers under its ‘Uncarrier’ brand; as well as by moving into new markets such as enterprise; and of course acquiring Sprint. But with two strong rivals, AT&T and Verizon, and potential challenges from the major cablecos and from new mobile entrant Dish, TMO cannot rely…