I think there is still a chance, mostly based on how his flames work, in my opinion
Zoro used advanced CoC when he was confronted with his dream
His dream includes
-Protect his captain with his life
-Get stronger and beat the considered world strongest swordsman
-Honor the promise he made to Kuina
These are tied, and cant't be untied, as we saw during 1033 when Zoro coats his blades with CoC.
If Sanji will get CoC (and consequently CoC coating, obviously) it needs to be connect to the All Blue somehow
I don't know how many power ups Sanji will get until EoS, but i really can't picture another power up other than a super future sight and possibly even stronger flames, but how will those flames be a thing? CoC coatin could be one of the options, but obviously that Oda can come up with anything he wants, especially the most unexpected ideas...