I think once WS-15 is ready they will add a "gun" since the space is there from day one. Whether it will be a gun in the traditional sense remains to be seen.
Given how J-10 and J-16 production is ongoing, I'd hope they don't add a gun on J-20.
They can put guns on future UCAVs if our estimate of 5 or so years before WS-15 reaching service J-20s then Dark Sword should be ready to be combined with the rest of the fleet, especially J-20S which already exists in at least prototype form if not further along in the program already.
In 5 years time, 6G comms will be old news and algorithms today are beating manned fighters and pilots in simulations. It's easy to program this in a simulator but much harder for a physical aircraft to deal with real world variable change to that degree but if they can't already do that today, they sure can in 5 years time. Some drones were already beating F-16 pilots in dogfights iirc. That may be under still controlled environments but the means have been there for some time.
I'd rather UCAVs get engaged in dogfights. They can pull crazier turns after all. It'll be much more effective once the algorithm side is there. With so much computing progress and machine learning, even autonomous driving have deeper and more difficult challenges than writing code for a dogfight.
A single competent programmer can probably already code the most undefeatable AI pilot on DCS. A team of the best engineers doing the same for a real life UCAV and given billions and over a decade to do it would be able to bring that into the physical realm.