Hi mike,
Always good to meet a fellow gamer.
you are right about the longevity of 40k, there will always be players.
If you played heroclix you will probably like 40K, although the scales of the games are different (an average 40k game has 60+ figures).
I recommend watching a few games of 40K to see if you would like and then perhaps trying a demo game. I have two armies and could teach you a game this Thursday after 5:30pm if you’re interested.
I also have a few mechwarrior clix also but nothing competitive. I played classic battletech much more.
-Pyro