Won't UAVs, with varying degrees of autonomy, be able to outmanoeuvre and outperform a fighter that has the additional burden of having to carry a pilot and all the extra hardware associated with that?
There is some scope for a manoeuvrers competition between the larger fighter class UAVs and current gen missiles, but the purpose built and smaller machine will always win the agility fight eventually so it doesn't seem like a very fruitful contest to enter from the perspective of the fighter manufacturer.
The only military advantages I can really think of manned fighters would be the increased situational awareness of a manned craft: the pilot has a panoramic view of their surroundings thanks to the fighter's canopy and being able to look around. Although, this seems like something drones could achieve relatively easily, providing a 360 degree view to their remote pilots.
Manned craft also have the ability to function autonomously if communications are down due to jamming, I guess? Drones could proceed toward a preselected target even without comms, of course, but a based on my layman's understanding of air combat decision-making is a huge element of combat flight. Things are messy, confusing, and ever-evolving.
Fighters are growing in size because engagement distances have massively increased thanks to the proliferation of high quality sensors and long range missiles. This ultimately means that the fighters need to have more range (fuel capacity), more powerful (bigger) sensors, more electrical generation capacity to power those sensors, and they need carry more and larger munitions.
For an aircraft that meets those requirements you can take the pilot out and you won't see many benefits. It's still going to be large and very expensive.
Smaller, cheaper drones can supplement this but they are not a replacement.