From the twitter blog: 

We're thrilled to announce that we've entered into an agreement with Atebits (aka Loren Brichter) to acquire Tweetie, a leading iPhone Twitter client. Tweetie will be renamed Twitter for iPhone and made free (currently $2.99) in the iTunes AppStore in the coming weeks. Loren will become a key member of our mobile team that is already having huge impact with device makers and service providers around the world. Loren's work won the 2009 Apple Design Award and we will eventually launch Twitter for iPad with his help.

I can only say congrats to Atebits. This is great news. But the question is: What will become of Tweetie for Mac? Will they maintain the app also or will it be discontinued? We'll just have to wait and see.