"For nine quarters in a row we have over 1 million [customers] added," he said in an interview on CNBC's "Squawk on the Street." "I'm pretty sure the yellow school bus [Sprint] is in the back."
On Thursday, T-mobile announced that it had added a net 2.1 million customers in the second quarter, up from 1.5 million a year earlier, helped by aggressive offers, and the company said it was adding services in Mexico and Canada.
The company unveiled its "Mobile Without Borders" plan, which extends calling, texting and 4G LTE data services throughout Mexico and Canada for "Simple Choice" customers—those on plans that unbundle equipment costs from service charges—at no extra cost.
The move is aimed at helping T-Mobile compete better with AT&T, the second-largest U.S. wireless carrier, which bought Mexico's No. 3 and No. 4 wireless carriers, Iusacell and Nextel Mexico, this year.
"The whole world of content is going to the Internet, and the Internet is going mobile," Legere said. "Everybody in any piece of that spectrum is going to have to figure out how to get all of their content, media and video to subscribers. I do a piece of that very well."
Legere wouldn't comment on the specifics of talks he is reported to have held with Dish Network CEO Charlie Ergen, but did say:
"I run a wireless company, and that guy is holding a pile of spectrum, am I interested? Yeah. He's also got a dying satellite business that would need to be fixed or moved. He's got some rights to content. I think it's OK. Is it the only thing I could do? No. There is a whole spectrum of partnerships in that array of what can take place."
T-Mobile is scheduled to report second-quarter results on July 30.
—Reuters contributed to this report.