Couple of years back I did a post on SIPTO (Selected IP Traffic Offload) and related technologies coming as part of Rel-10. I also put up a comparison for SIPTO, LIPA and IFOM here. Having left it for couple of years, I found that there have been some enhancements to the architecture from the basic one described here.
I have embedded the NEC paper below for someone wanting to investigate further the different options shown in the picture above. I think that even though the operator may offload certain type of traffic locally, they would still consider that data as part of the bundle and would like to charge for it. At the same time there would be a requirement on the operator for lawful interception, so not sure how this will be managed for different architectures. Anyway, feel free to leave comments if you have any additional info.