Find it nearly impossible to believe he'll never play again. If Peyton came back from not even being able to use his arm, I think Luck will make it back. People - the media - just like to sensationalize things.
That said, Brissett doesn't look like a bad alternative. There are a few things to be optimistic about with the Colts. The d-line is finally legit (MLBs are an absolute joke), Simon and Sheard are pretty good edge rushers (need one who is elite), the no-name secondary has been pretty good (albeit against weaker competition).
On offense, it all comes down to the offensive line being a disaster with injuries and guys who haven't lived up to expectations.