As of present, there are the E-767 AEW&C aircraft and the KC-46 tanker aircraft, both of which are based on the Boeing 767 family airframe.
On the other hand, it'd be very interesting to see what the next generation of ELINT/SIGINT, EW/ECM/ESM, and MPA/ASW aircraft using airframes of a similar MTOW category as the 767 family (~140-160 tons) would be like (and how they would perform relative to their Western counterparts).
A 767 class aircraft for ELINT/SIGINT, EW/ECM/ESM, could make some sense especially for the PLA as the extra range means they can reach out into the pacific and loiter when flying from mainland PRC bases (which US 737 and 707 based airframes do not suffer from as much given they operate from bases closer to the PRC mainland).
I've toyed with the idea of a Y-20B based ELINT/SIGINT, EW/ECM/ESM aircraft for that specific reason (because a 737/C919 sized airframe would probably be a bit small) -- but a sino-767 airframe would of course be much more optimized for that role if it existed.
OTOH a 767 sized airframe for MPA/ASW does seem to be a bit overkill if it's operated in the traditional manner. It may well be that a 767 sized MPA might leverage MALE UAVs in the MPA/ASW mission to make up the numbers a little and provide closer in support (the MQ-9B class WL-X UAV of course is offered with meaningful ASW packages, as well as various other UAV projects that could be suitable for adaptation).
But really the most tantalizing prospect is if this is a 767 class aircraft, is its applications for tanking. The Y-20B MRTT (and YY-20A) are fine and good, but a twinjet widebody esque airframe is far more optimized for the tanker role than a transport airframe is. And the mass procurement of such an aircraft naturally means eventually the Y-20Bs won't have to take on the tanking mission (even though they're capable of it) as numbers of a "sino-767-tanker" grow, meaning they will likely focus on being strategic transports... and as evidence in recent times has shown, one can never have too many strategic transports, meaning whatever "excess" Y-20Bs they produce will still very much find a home/role in future even if a sino-767-tanker flourishes.




