GPL v2 versus GPL v3
Regarding GPL for future versions - I think the challenge is exactly that though i.e. removing major parts of future kernel releases by claiming copyright of your previous contributions and rescinding use of your code without permission so it is NO LONGER covered by GPL version 2. They cannot use code that is rescinded in future so that basically halts a lot of development until completely alternative code is redeveloped to cover the missing bits. Maybe a good time to move the Linux kernel to GPL v3 which explicitly removes the option to rescind contributions but unsure that is possible to apply retrospectively.