Love them or hate them...look at Glocks, specifically the Glock 17. Between the Gen 1 and the Gen 4, there really aren't any drastic changes. Most changes were cosmetic, and some internal parts were slightly upgraded. For the most part, the Glock 17 is very much so the same now as it was in 1980s. Here is an article that explains each Glock Generation.

My point is, Glock has been selling the same pistols successfully for decades now. I did some "google-ing" and the most recent number I could find was 9,000,000 Glock pistols produced between 1980 and 2013.

These firearm manufactures know what they're doing....except for Colt, but that's for another thread. As mentioned in previous posts, if there is high enough demand then keep selling them. There is nothing wrong with upgrading pistols over time, as long as you can sell them. As with most businesses the bottom line is profit.