You're missing the point. Player counts for that game dived because despite fairly regular new content and replay value, the meta and power creep pushed all players into using very similar functioning builds with everything that could be considered an alternate playstyle being so underperforming many people couldn't even make them work in the 2-3 difficulty range. HD2 has much better variance in maps and enemies, so as long as devs keep the trickle of new content and powercreep under control this game easily has a 6-8 year shelf life. Community will trickle downwards like all games do as they age and new games pop up. But as long as the devs don't fall into the trap of caving to vocal minority of players demanding any exploits they find stay in the game, we could easily have 100k-200k regular pops a year from now.