Well FWIW T-Mo is already rolling it out to the S5 so it might be coming for the Metro S5 before too long. Dunno about the S4- maybe, maybe not.
But either way you may not want to be in such a hurry to have it. Lots of problems have been reported with 5.0 and people have been reverting to 4.4 (at least those who can) or trying to.