They likely arent missing the playoffs, worse case they are 4 ahead in the loss column after today while holding the tiebreaker and 17 games remaining.
If the Cubs go 9-8 in those 17 games, to miss the playoffs the Padres and Diamondbacks would both have to finish 15-3 or better to knock the Cubs out. Also, they still play each other 3 times, so one of those teams is taking 2 losses at least, meaning they'd have to go 15-1 in their other games to knock the Cubs out.
Even if the Cubs really flatline and struggle, let's say 5-12, the Padres and Diamondbacks still need to both go 11-8 or better, with the of the teams needing to go 11-6 or better because they are getting 2 losses from the other one.
I mean it's possible, but not super likely at this point. If we didn't hold the tiebreakers over both, or if one of the teams was much closer to the Cubs, I might have some concern because then it only takes one team getting hot to knock us out with an uneven finish