Is killing Severide the only way to properly write him off Chicago Fire?
Let's make things very clear: we don't want to see Kelly Severide (Taylor Kinney) get killed. It would be a sad day for Chicago Fire fans everywhere. But the way things have been going with the character, and his diminishing involvement with the show, means that death could be a very real possibility.
There are only so many directions to go in IF Taylor Kinney decides to leave the show, and we can look at the handling of other actor exits on One Chicago to see how they went over. Firstly, Severide could decide to leave Chicago and start a new life somewhere, which would mean divoring Stella Kidd (Miranda Rae Mayo).
Severide is in a tricky spot narratively
Doable? Sure. But Chicago PD just attempted something similar, in terms of one half of a married couple leaving the show. Jay Halstead (Jesse Lee Soffer) moved away from the Windy City within a year of his marrying Hailey Upton (Tracy Spiridakos), and while they stayed together for a bit, the long distance gambit failed and they eventually divorced.
Most PD fans are not fans of the way the Halstead and Upton marriage ended, and splitting up Kidd and Severide would be more of the same. It would diminish the years that were spent getting them together, and the things they had to endure along the way.
The show could go the spinoff route, and give Severide his own arson investigation show, but there are two issues with this one. Chicago Fire showrunner Andrea Newman has already nixed that plan, and if Kinney wants to leave the show, the odds are slim that he would accept a bigger part within the same franchise.
Severide's future on the show is unclear
An unexpected death would preserve the Stellaride couple in the minds of fans, and allow Kidd to remain at the forefront of the show. It would also resolve the somewhat uncharacteristic decision Severide would have to make to leave his home after decades (even if likes to go on the road a lot lately).
Obviously, we'd rather the Chicago Fire writers not be put in the difficult position of having to write off the character. The best case scenario would be to have Severide return to the show full time, and turn his passion for arson investigation into something he can do within the confines of Chicago.
Neither Kinney nor the show's producers have discussed long term plans for Severide, so we will have to wait and hope that he sticks around. If the character bites the dust in shocking fashion, though, don't say we didn't warn you!