Couple of things to address. No, they are not going to quit making Gen 3/4/5 parts unless lawsuits make them. Why do people think that Glock relies on the LEO market? While it certainly is important it's not the majority of their sales. Was talking to a Glock rep a few weeks ago and I believe that number was a little less than 30% and the civilian market was the remaining 70%+. Yes, Glocks sell well to PD departments, but Glock sells around 350k handguns a year but for the Gen 6 that number will be much higher. It is not possible that PD are buying that many weapons and the military predominately buys the Sig P320.
There are 737,000 law enforcement officers in the US from state, federal, and local law enforcement departments. Not all of them use Glock but 65% of them do. So, doing the math that number is 479,000 total LEO officers carrying Glock. The typical replacement cycle is 5 years but I've heard some departments have a cycle of over 10 years but for simple math we will choose 5 year replacement cycle. 479,000/5 year replacement cycle = 95,800 per year. That's less than 30% but they will buy a few extras to have on hand to get them to the 30% number. 107 million US citizens own, at least, one firearm and many of those buy Glock as it is one of the best selling handguns in the US.