A tweet from MG Siegler has started the rumor mill flying tonight with news that Twitter is set to discontinue development for their Twitter for Mac app, but it will still be available to users:

Word is that Twitter made the call today: Twitter for Mac is done. They won't kill it outright, but no further updates. Goodbye, old friend.

Twitter for Mac started out after Twitter purchased Tweetie and turned its Mac client into the official Twitter for Mac app. One of the biggest complaints fans of the app made was that Twitter didn't bake in support for the Retina-powered MacBook Pro.