After re-reading the last couple chapters I think there is a very real chance that Sangi is getting the Mera Mera Fruit..
This could be just because who he has fought but right now there seems to be quite a difference between Sangi/Zoro. Of course Zoro has always been stronger but now it seems like there is a much larger gap between Luffy/Zoro and Sangi/Franky seem much closer to each other in power.
That coupled with the fact Sangi has used Diable-Jambe in pretty much every fight means he's either being pushed to use it every time or he has some unknown technique that surpasses it, and thus now the diable-jambe uses less energy to use (I think this is a real possibility but I wouldnt bet my bottom dollar on it).
Idk, overall I think he could get it and not be stronger then Zoro, which in my mind makes it like a real possibility.