Well, it could happen, but I think it's unlikely, lv 5 is suposed to be an extremely exclusive club, accesible only to those who completed complicated requirements (until Xanthe started forging invitations), moreover, Aos said something like the MC would truly understand how fucked up his situation is once he reaches said level, so it could be reserved for later. Also note that a lv4 MC could be very well be on par with the newer lv5s, especially with the Eye now active, so there could be no need for him to evolve in the short term. So far our protagonist has evolved from human to lv 3 (soon to be 4), the next part could start from lv4 and have him acquire alternative ways to increase his Power (as Nico has hinted at), like Deryl's "Philosopher's Pebble", Ella's eyes or the DW sword that we haven't heard from for a while, then reach lv5 (preferably through natural ways, Xanthe's serum if failed decisions and/or checks, and finally that "different" stage that he is supposed to get to (like that statue in the sky city, idk if he would skip lv5 to this one).
(Then again, he could die and be reborn with the help of Nyx's mark, though this might be just a trial.)
