Stiker fired IDPA guns are a submarket of a submarket. They are popular here, but not in some sort of global firearms sales sense.
S&W and Glock have been sabotaging themselves for long enough that HK is guaranteed to sell a fair number of guns just to folks who are tired of guns that may or may not function, group or break. The M&P is 9 years old, and may have just gotten its accuracy problem fixed - ignoring the fragile striker problem or the original breaking trigger problem.
Folks know that isn't the kind of public beta testing HK engages in.
I don't know what all the griping is about. HK chose what they wanted to produce and when. They didn't lose out on some sort of development time - their competitors have been dumping half engineered crap on the market for years and sales seem fine. Maybe HK didn't do a striker plastic gun because they didn't want to be associated with all of that garbage.
Alternatively, HK took the mechanical disadvantages of striker fired recoil operated autos too seriously to go play on the dark side, until know.
It doesn't really matter: The new gun will work very, very well and sales will be brisk enough to make it worth HK's while. And folks who want a real military grade firearm, rather than S&W and Taurus's "great warranty!" range toys have got something to buy, now. It's a win for everyone when the best quality companies bring their show to town.