Player pool's been decreasing for years, and that's not gonna change, but its never gonna fully die until Bannerlord's release. But be realistic aswell, Gaming in public servers is since matchmaking's decline, hopeless, and that's why 90% of the players taking part in NC didn't really play out of Scrims/Officials. Tournaments are still fun & competitive and people are gonna keep playing them, specially if we meet another scenario where teams are balanced or there's a purpose behind winning the games.
The focus on the upcoming tournaments should be rapid formats where big quantities of matches happen in a short period of time allowing a fast-paced system so teams are motivated to actually play the game, if the games come this way and competitions are properly organised, it could potentially push IG/Matchmaking a bit further as players would use it again for warm up/practise(or mere fun) for a short period of time.