I think out of ORD what you will see is the 76T airframes getting made into 756 airframes, and the flying transitioning over as that happens.

So, over this winter you will see the 76T base shrink and disappear and a like sized 756 base grow in its place.

Right now out of ORD the 76T folks fly to LHR several times a day (3 for most of the year, but sometimes 1 of them is upguaged in the summer to a 777) they also fly to AMS. In the winter they have historically gotten MUC, CDG, and BRU back from the 777 as well.

I would suspect that the base will actually be slightly larger than what you see on the 76T right now as the total amount of the flying will become more stable on a monthly basis. You will have MUC,CDG,BRU and 3 LHRs during the winter and then in the summer when some of those get upguaged, you will get the seasonal flying of EDI, SNN, etc to balance it out.