A big change happened at the end of Chicago P.D. Season 6, although fans who haven't kept up with casting news may not have known it at the time. Jon Seda, who was part of the Chicago universe since way back when it was comprised of only Chicago Fire, was announced as departing P.D. following the sixth season finale.
The episode didn't give him much of a goodbye, but Seda himself shared a touching farewell message with fans about his time as Detective Antonio Dawson:
It’s been an honor portraying Det. Antonio Dawson in the #One Chicago world. To my cast family, I’ll always treasure the time and stories we shared. To all you #chihards out there, THANK YOU for being the best of fans! We’ll Always have CHICAGO.
Jon Seda showed no bitterness in his Twitter post about the end of his time as Antonio Dawson on Chicago P.D., which actually came only one season after Monica Raymund departed the Chicago universe as Antonio's sister Gabby Dawson. Monica Raymund's departure was written into the show as Gabby finding her true calling in Puerto Rico, which sadly meant leaving Casey behind. Antonio wasn't given quite so clear a sendoff from his Chicago series.
In the Chicago P.D. finale (which I rank as the best of the three Chicago finales this past season for a number of reasons), Antonio's final scene consisted of preparing to take a pill in his car. He wasn't dying, packing to join Gabby in Puerto Rico, accepting a new job (which is how P.D. explained Erin Lindsay's absence after Sophia Bush's controversial decision to move on), entering rehab, getting arrested, or anything definitive.
Hopefully the Season 7 premieres drops an explanation about what happened to Antonio that he's no longer part of the unit. After all, despite Jon Seda's very temporary move to Chicago Justice, he was key to the foundation of P.D. It's not out of the realm of possibility that Seda could reprise his role at some point, although I wouldn't put money on him turning up in the Season 7 premiere. At this point, I'm just hoping he wasn't killed off off-screen!
When news broke that Jon Seda would be out for the 2019-2020 season, reports indicated that Antonio Dawson was considered to be "played out" as a character on Chicago P.D., which is a marked difference from why Gabby Dawson was written out of Chicago Fire.
If a storyline invites the return of Antonio -- even if only for one-off episode or guest arc -- fans could see him in action again. The ratings for all three Chicago shows could mean they stay on the air for a while yet, unless they drop off significantly in the coming TV season.
Find out how Chicago P.D. explains Antonio's absence when Season 7 premieres on Wednesday, September 25 at 10 p.m. ET on NBC. The Peacock Network is continuing with the all-Chicago block of programming, with Chicago Fire kicking off in the 8 p.m. ET hour and Chicago Med (which went through some casting changes of its own) picking up at 9 p.m. ET.