It's only week 2 of the season, but Bull and MacGyver both did well in the ratings despite horrible reviews for both. Reviews definitely don't matter when it comes to ratings and viewership.
Right now, it doesn't appear either will be pulled before the end of the year. Their ratings would have to absolutely collapse to sub-1.0 (unlikely at this point). And even then, at the very least, they'll finish out their initial 13 episode orders.
CBS isn't going to suddenly pull any returning series either. The returning show most at risk is 2nd season Code Black on Wednesdays at 10pm. We'll see how it does tonight. But even then, it's unlikely to get pulled before December.
Most likely earliest scenario is the Wednesday 8pm slot between Survivor seasons. And they could easily premiere it the week after Survivor ends, even if it'll be Christmas week, just to squeeze in the 12 episodes before a possible Wednesday, February 22, 2017 Survivor premiere. If not, then a January premiere in some other slot. But before end of 2016? Probably not.