I’ve often wondered how kids think about that as well, and it was discussed at interesting lengths in this thread…
http://talk.collegeconfidential.com/musical-theater-major/1318265-what-future-are-our-mts-training-for-p1.html
I bet like so many aspects of this business the “correct” answer probably depends on who you are. I’ve seen athletic boys with no dance experience get to a not-super-dancy National Tour level in 4 years of college, but am not aware of any non-dancing females who have become consistently-employable dance ensemble members at top theatres in 4 years. Does anyone have examples of that happening? All of the MT kids I know started college as relatively strong singers, so I don’t know if similar things could be said about singing or not.