It's a good thing that Station 19 has already been renewed for Season 4, because the Season 3 finale looks explosive (literally). In the preview, Robert Sullivan is in surgery and five firefighters (Dean, Jack, Vic, Ben, and Travis) are trapped in a building with homemade explosive devices. Any one of those characters could fail to make it out of Season 3 alive or have their fate become a cliffhanger to resolve next season.
Fortunately, the wait for more episodes shouldn't be too long. According to The Hollywood Reporter, Station 19's fourth season is likely premiere this fall, provided that production can safely resume this summer. This schedule change would allow it to continue the Grey's Anatomy crossovers that have made it so successful: after Grey's Anatomy showrunner Krista Vernoff began showrunning Station 19 too, one of her first moves was integrating it more with the original series. Now the two cross over almost weekly, giving fans more incentive to tune into both. Station 19 airs at 8 p.m. on Thursdays and Grey's comes right after at 9 p.m., which has, according to TV Series Finale, helped Station 19 become ABC's most-viewed scripted show (yes, even above Grey's Anatomy). Between Season 2 and Season 3, it had a 22.8% growth in viewership. No wonder ABC was so eager to renew it.
Though Station 19's third season aired as a midseason show in January, bumping it to a fall will allow it to air alongside Grey's Anatomy and continue the crossovers. Based on previous premiere dates, both shows will likely return on Sept. 24, 2020 if they can begin production in late July. That may not be possible amid the COVID-19 pandemic, which could lead to a slight delay in both series' returns. But whenever they do come back, expect them to do so together.