It's pretty much confirmed he returns next season seeming Maya Rudolph will guest star as a runner whom Brian falls for. Also the fact there are two future episodes this season with Brians name in it.
I HAVE to watch this episode; seems as though it's a "jumping the shark" moment. Brian was such an intricate part of the series, for me anyway, It'd be strange for him not to be there anymore. But I suppose, what's done is done.
It's the same car Brian has. Maybe this time-traveling story didn't end. I believe Brian killed himself (or his alternate version) in another time travel accident. Look for the next episodes. There are still episodes featuring Brian. The season finale will be called "Brian the Closer". I strongly believe Brian isn't permanently dead. We never know what's on these writers mind