Well, at the start of the "Block" era, it was obvious that the demand for 1911's was still there and growing. Plastic pistols are a dime a dozen (more or less) these days and the search for the newest greatest "wonder nine" still continues. Case in point, look how Sig Sauer has no misgivings about making its latest offering obsolete within a few months of it's release. (and fixes). Seems there IS a lot of risk with new plastic designs as everyone tries to change the plastic just to have something "different" from the masses.
The 1911 on the other hand, just seems to keep having the original design refined, not made obsolete.