Upgrade 7D + 17-55 2.8 to 5D MkII + 24-70?

I do mostly low light work, like weddings and stuff but also sports like surfing, and I really like my setup. The IS on the 17-55 is wonderful. I do not shoot studio work.

I also own 10-22, 70-200F4IS, 100-400 and 400 5.6L.

As far as I know, the 5DMKII is a stop better in low light, but the IS of the 17-55 probably makes compensates the difference. I can easily shoot at 1/20 with the 17-55 with max zoom (88mm equivalent). Not really worth shooting slower because people move. This would not happen with a 24-70.

The focusing system on the 7D is also better than the 5D.

In a couple of words: Is it really an upgrade for what I do?