So now we know the Colts don't want to keep him as QB3.
Best chance, he clears waivers and ends up on the Colts PS tomorrow. According to reports, they are expected to sign him.
https://cbs4indy.com/2019/09/18/colts-waive-quarterback-chad-kelly/
However, there's an off chance some other team takes him.
https://www.redcuprebellion.com/2019/9/18/20871760/ole-miss-football-chad-kelly-colts-saints-jets-broncos-steelers-jaguars-brees-bridgewater-darnold
Third option, he could clear waivers and sign to another team's PS. I don't think that's very likely either.
And of course, there's a chance he could end up totally unemployed. Despite the posts in this thread, I think that is probably the least likely outcome.