The problem with cycling without other training is that it can create an imbalance between strong quads and weak hamstrings. That puts you at risk for an ACL injury. Cyclists also also tend to develop stiff backs and weak upper bodies, neither of which is good for skiing.
since i started road biking its hard to make my legs tired MTBing, my upper body normally craps out first that normally happen at like 20ish mile at cruising pace.
ACL injury, I am pretty sure my chance are pretty low