Most of the plot points in SO are not even at the middle of their development and some(looking at you purple haired girl) did not even start, while others ended on a very poor and rather fucked up not intended that way note(like poor Sora had her final point end). It will not be that hard to continue SO where it ended, it would work even better if last updates which turned girls into lizardmen would get scrapped and everything would begin again from the "graduation day" plot point, which Happy Mori even foreshadowed by saying that she still cant believe school year repeats itself.
It is not that very hard to keep SO line according to general idea and themes made by Personas, but it would still be better if he finished it himself. If the likely scenario where author cant finish his own work comes to pass, then hopefully SO will receive "The Wheel of Time" kind of treatment in the near future.