I was thinking the Bears were holding out until MIN in Week 5 on Monday Night to give Trubisky maximum time to prep with the #1s, but the more I think about it, I believe they will go for next week vs GB.
I don't care if it is a short week, it is a short week for GB and they would have very little time to prepare for Trubisky, so in a way, next week would be better. Surprise everyone and announce Trubisky the starter on Wednesday and let GB scramble with a new defensive game plan, because if they are expecting Glennon, they will not plan for contain/spy or for roll-outs or bootlegs.
So I say put Trubisky in Week 4 if Glennon has another sub-par performance against PIT. I don't really know how to assess PIT because they beat CLE and MIN w/ a backup QB.