Manchin may indeed switch, but he still is quite liberal (a 74% leftist rating for the duration of his time in the Senate). The GOP’s most left-wing Senator is ME’s Susan Collins (and her lifetime rating is 52% leftist, though she has scored 72% leftist in 2013 and 80% in 2012). There’s also talk he may leave the Senate entirely to run for Governor again in 2016 (which would force a special election that the GOP would almost surely win).
Add to that, Maine’s “Independent” Angus King, a very left-wing member (87% leftist) has indicated he wants to serve in the majority, and hence would vote to organize with the GOP, so there’s 2 gains numerically (though certainly not ideologically).
Ideologically, the GOPe is more aligned with King than Cruz. The lily-livered quislings running the GOP had better learn how to lead. It will take a seriously long and bloody fight to get any conservative legislation through and even then, Obama is going to veto everything.