Can't confirm, but i'm pretty sure you will be able to advance the storyline beyond lvl 100, even if you won't make it before Phase 2 begins. I assume the only thing you'll miss is the Extra Stage with tons of Boss Encounters and Stamp Chance rolls people sit in after they clear lvl 100 during Phase 1, waiting for the beginning of Phase 2.
Still, i wonder, if i'll ever be able to play gambit 1 again to read it's storyline... ?
Stopped playing all Nutaku's games (and, thus, using HBC and other related forums) around 06.2016