I thought it had to do with future updates to twitter for mac. for example.
The box somewhat similar to the dropbox icon. Some sort of dropbox support?
The linkage one could have something to do with linking the iphone/mac apps.
I originally thought that that message was hinting towards the next bundle as well, but when you mentioned the "linkage," I think you may have hit the nail on the head. Loren, the developer, said that that was one of the big features he was building into the framework. Obviously, it's not enabled yet but, If I remember correctly, he said the basic functionality is already built in to tweetie 2/twitter for mac and the IOS app.