By Marina Lopes NEW YORK (Reuters) – T-Mobile US expects to engage in some form of cellular industry consolidation, the CFO of the United States fourth-largest carrier said on Monday, boosting investor expectations that a merger with Sprint Corp could be on the horizon. It is not a question of if, it is a question of when, Braxton Carter said about the companys prospects for consolidation at a media, internet and telecom conference. The comments come on the eve of an address by the president of SoftBank Corp, which owns 80 percent of Sprint, to investors and technology policymakers in Washington on Tuesday. Hopes for a merger between Sprint and T-Mobile, the No.3 and No.4 U.S. mobile service providers, faded last month when reports surfaced that the U.S. Department of Justice and Federal Communications Commission would look skeptically on a merger.