There is litte connection between leg length and cycling performance. There is, however, a large connection between the ratio of leg length to torso length and musculature. Typically, men with relatively short legs compared to torso length more easily develop muscle mass. Long-legged guys would be more prone to develop strength and tone. This is far from being universal, but a guy with long legs/arms would have to do specialized weight training focusing on one part of the range of motion to obtain any significant mass.

Therefore, when you just look around it's easy to see that guys who naturally sprint well have larger quads and a smaller leg length to torso ratio. (see Robbie McEwen or Mr Zabel) Climbers often are often build like Lance or more frequently like Tyler Hamilton, with small bodies, lithe builds and a pretty even leg to torso ratio.

There are so many exceptions that are overcome by talent and training that it's impossible to predict however. Lance himself was originally known as a sprinter. Jaja too. Mario Cipolini has relatively long legs. So you never really know.