I am thinking more and more that Luffy will clash with Saturn, be pushed back, and then be rescued by the robots or giants going by these spoilers. If Saturn has a whole other transformation, then Luffy is not taking him down in like 1 or 2 chatpers. Oda does not write fight/characters this way.
The idea some people have of Luffy "squashing" Satrun like a bug as this seems to imply: Could perhaps work in theory if you think Egghead lasts a lot longer than it currently looks like. But the way things are shaping up, I doubt such a scenario.
My guess? Oda does as Oda likes and teases Saturn's strength via his clash with Luffy, but not much more. He will push Luffy back far enough that he can run away with the rest of the crew while Saturn deals with the giants and robots. Then we might cut back to Saturn having won offscreen twenty chapters down the line. I hope this won't happen since I would like a bigger conclusion, but I think this is going to be it.
With the potential release of the Void Century info via Vegapunk, it seems likely that this will be the big event of Egghead rather than Saturn dying or going down against Luffy, but I guess we will have to wait and see.