You heard that right, as of April 9th Tweetie will be the official Twitter app. Loren Brichter was the lone developer behind both Tweetie apps, and he will continue his innovative work as a Twitter developer. If you've never used Tweetie 2, check it out when they relaunch it for free (it is well worth the $2.99 now, however). It is an amazing Twitter app, not to mention an amazing iPhone app in general, setting the bar high for any iPhone developer. Here's a snippet from the atebits website:
I’m happy to say that as of today Twitter is the proud owner of Tweetie - and I’m joining their mobile team and starting work on turning Tweetie.app into Twitter.app, for iPhone and iPad.
Tweetie 2 for Mac was close to being released and the beta was going to be released to MacHeist users. This seems to be unchanged.