The latest intel sockets remain for two cpu generations:
1155 - 2gen Sandy Bridge and 3gen Ivy Bridge.
1150 - 4gen Haswell and 5gen Broadwell.
1151 - 6gen Skylake, and almost sure 7gen Kaby Lake.
It has some relation with tick/tock roadmap, but they have just changed to a Process/architecture/optimization, so there can be a 3gen socket in the future.
But you can still find/buy older gen CPU's if you need to replace for a specific socket.
Regards