Unless they've recently changed thing, there is not a stated limit to the number of carry-on bags (and if there is, it's certainly not limited to just one because I know we always have at least two).
Mater-of-fact, we once packed lightly enough for a 4 day trip that we were going to just carry all our luggage on. A CM did convence us to check some of the baggage rather than carry it all, but they never told us that we COULDN'T carry our luggage.