Since NGS was made to sit alongside current-gen PSO2 Meseta; you can transfer characters back and forth between them at any time. They will be applying the graphics engine upgrade to the first PSO2 as well so it will continue to exist alongside NGS and not only be abandoned.

They likely figured that individuals would wish to be able to experience the first PSO2 how JP players did so that, when NGS comes, they might experience precisely the exact same context that JP players had/have. Basically, they wanted to provide folks a chance to experience the prequel prior to the set-1000-years-later sequel (of sorts) launches. They've also expressed that they need JP and NA to eventually be in sync, so this provides a path so that NA players can arrive to that exact same point as JP players in an more-accelerated way.

You could look at any given F2P game cynically in that sense -- the sole reason to start any F2P match (or game, really) is to break-even or ideally profit. But if they had only started NGS without bringing through the first PSO2 at all, there'd be a good deal of articles NA players would be missing out on, which includes items you may get in cheap Phantasy Star Online 2 Meseta  and carry over to NGS. (Which is why even utilizing Tweaker and playing the JP servers wouldn't be the same, since you couldn't take any of the over to NA servers.) Plus, given that they chose original PSO2 is going to stand alongside NGS, they were going to have to vent both over anyway, so better to do it in phases.