Henry gone the defenses don't or won't be nearly as fooled on the play action. They will also not have to defend the run as intensely causing harder passing completions. Henry will definately be missed regardless of how good that OL is.
stats show that play action still works even when the run game is weak. It’s like pretending to punch your friend in the nuts. Of course he’s going to flinch even though he knows you likely aren’t going to actually do it. Play action is only designed to get the defense to flinch for a beat.
Look at the revolving door at RB for the 49ers. Their play action game is still effective no matter who plays RB.
Losing Henry doesn’t mean their run game will go from great to awful. It doesn’t mean you go from run heavy to passing 50 times per game.