I wouldn't panic, IV's multiplayer is still up.
Red Dead Redemption had a new update as well. The only thing I've noticed is the Social Club no longer features an online 100% checklist or other options.
As long as they don't pull the plug on IV's multiplayer anytime soon, despite the levels, then fine by me.
How many still play IV's multiplayer? Even though V Online is out, have always wondered after 5 to 6 years of playing the game.
Well one lobby I joined still had about 6 players in it, so I'm guessing a good number.