Later than 2.0 (read as Two Point Oh or as Two Point Zero)
Linus and all other Core Developers will not even accept anything but 2.0 patches or add-ons.
In fact, if you look at the sign off checklists being developed to un-tangle this problem, you will see a point for 2.0 only. Anything else fails and will be rejected.
GNU GPL v2.1 or v3.0 will become the worst thing since Microsoft Bob. The GNU-Tools will be forked and continued under v2.0. I guarantee it. IN fact many of the problems with the GCC toolchain, will be fixed and work better.
The GCC Tool chain once forked will take all "super powers" away from the FSF and they will never be able to get the horses back in the barn.