There is no way they can make any huge changes/reboot at this point. SS is fine. WW and JL1 are in production. Aquaman, Flash, Cyborg and Black Adam have all been cast and some presumably have solo films in some level of production. I could see a lot of behind the scenes changes in terms of producers and writers if BvS has a lukewarm box office reception but I doubt they just start the whole thing over.
Yep, there's no way.

No way at all.