Chengdu's made clear they want the J-20 to evolve into a family of aircraft.It is likely that J-20 w/ WS-15 will see some structural differences but I would be surprised to see J-20 with that extent of modifications.
There have been studies of such a configuration before with a "not-J-20 aircraft" shown as a representative for what I believe was a damage simulation study. But at this stage I don't think we have any evidence that there will be a J-20 with such a large modification in the future.
The biggest problem for the J-20 to be further upgraded is the lateness of the WS-15. We've heard nothing out of the rumor mill of late, and we have so-and-so aircraft engine manufacturer declaring they'll build around 5 WS-15 in the 2025 to 2030 timeframe, which is way too slow.
One big issue is the sizing of the J-20's current inlets. The airflow under the present DSI system is adequate for an Al-31 / WS-10X classed engine, but the airflow is insufficient for a F135 / WS-15 class engine.
The easy solution is simply to adjust the DSI; i.e, reduce the size of the bumps (and possibly increase their length) to accommodate the greater airflow needed, but an alternative solution would be to enlarge the inlets, creating greater body space and potential for the engines to be shifted to enlarge the weapons bay.
The measurements of the J-20 inlets are roughly the same, perhaps a bit larger, than on the Su-27 series for the Al-31 engines. It's a bit of a pity, to an extent, since larger inlets would have guaranteed better high-altitude / high-speed airflow, sufficient to allow the J-20 to have at least sustainment (requires afterburners to break Mach barrier, but can supercruise around Mach 1.3 without afterburners) supercruise. But that'd compromise low-altitude maneuverability as you'd end up with spillage drag from overflowing the inlets.