rbmartin,
I think we need to see how serverely our trains will be cut, but I assume that it is not off-peak where the pressure will be. I suspect that for a couple of years we will have one or two less trains in the morning and evening peak. The RUS recommended increasing the length to 12 carriages, but Network Rail are only doing platform lengthening for 10 carriages in the short term (they'll probably need to extend them again for Thameslink, but I assume that is a different budget). So there will be less capacity once they start cutting services in 2013.

In fairness, it is our line into London Bridge that can easiest absorb cuts to services, on a temporary basis, as we have the ELL (at least for people with travelcards, not Rail Only season tickets - like me). It will be a squash whatever cuts take place. But at least there will be benefits when we get the Thameslink service taking us directly to Kings X.