I can only hope that, if true, it's to make room for Twitter for Mac 2.0, rather than to convince people to sit there with Twitter.com open, hitting "$x new tweets" every few minutes.
I have the Twitter for Mac client open all the time at the right edge of my 2nd monitor, and if they get rid of that, I'm just going to lose the habit of following Twitter.
Given the least of several crappy choices, I would rather see in-stream ads in the native Twitter client for Mac if it means they continue developing it..
I'm in the exact same situation. I try to use the iOS client, and that works alright (much better than other apps I've tried), but I think you hit the nail on the head:
> if they get rid of that, I'm just going to lose the habit of following Twitter.
I'm not very good at tweeting. I try to make an effort to be part of the scene, to connect with my peers and colleagues, etc., but I'm just not that big of a Twitter guy. It's not for lack of effort.
Having the small, unobtrusive Mac app makes it so easy for me to see those relevant conversations and participate in them. If the app is discontinued, I would desperately search for a replacement before closing my Twitter account. If it's just a lack of active development, that's not as huge of a deal--I kind of like the app the way it is.
Again, I can only hope Twitter developers realize this, and have something new and better planned.