Just cause Viz has the license and isn't releasing the first volume until summer 2019 (according to the announcement at least) doesn't outright mean the translators are going to stop.
For instance, Sleepy Princess in the Demon Castle, another Weekly Shonen Sunday title and one that Viz has been releasing volumes for since summer this year, are about to get to volume 4 next year (the one with the Komi-san crossover chapter and I can see them using it as a means to further promote the manga half a year before we get it officially), and I still see chapters getting translated and uploaded to this website.
Translations could potentially stop at any point for it, whether it be the translators just not doing it anymore or if Viz (maybe Shogakugan too) send a cease notice and then they'd have to stop or face legal actions and so on.
Have they stopped yet? As far as I'm aware they haven't so we're likely to still get chapters of Komi-san translated even after the English release starts happening.
Unless of course the translators stop or get a notice to stop doing it but we'll just have to cross that bridge when we get there.