Strauss forces him to perfom repairs on cheap carnival rides whenever the circus comes to town. If he makes eye contact with curious mortals, he gets locked in a cage with fifteen horny szlachtas for the rest of the month.
Otherwise, he is only kept around for the occasional piece of esoteric advice that only a former Prince could afford to a newly-appointed ruler of a city of Camarilla interest.
Pinched from his page on the White Wolf wiki:
"Prince LaCroix's recent destruction is referenced to in the novel Gehenna: The Final Night, the first book of the Time of Judgment Trilogy and the final Vampire: The Masquerade novel. Thus, the appearances of Smiling Jack and Beckett (and possibly Caine) occur in Bloodlines before their appearances in the Gehenna novel. "
I've never actually had the chance to read the book so don't know if anyone else can confirm/deny/provide any more info on how he met the Final Death?
Realistically, I think that LaCroix was been swiftly substituted with some other competitor to the Prince throne.
After all into the Camarilla these things happen with regularity, if the holder of the place show incompetence (and LaCroix will be shown as a very incompetent and dangerous Kindred due his own actions, and greed) is a matter of hours, maybe days before he will be impaled and sent into ashes, then another Kindred will take his place.