T-Mobile CEO John Legere may want to make sure his résumé is up to date. Unnamed sources tell Reuters that Sprint parent company SoftBank is already in talks to buy a majority stake T-Mobile US from Deutsche Telekom for $20 billion, a little less than the $21.6 billion that SoftBank paid for Sprint. However, just because SoftBank makes a bid for T-Mobile that doesn’t mean U.S. regulators will allow the deal to go through, especially if they conclude that it will hurt competition in the wireless space. What’s more, a proposed Sprint-T-Mobile merger would come during a time when T-Mobile has really started making waves in the wireless industry with its aggressive “uncarrier” moves that have put pressure on incumbent carriers to change their policies about early smartphone upgrades, among other things.