Assuming this isn't a just a rumor, this reeks of corporate politics. Loren creates an app that gets peoples' attention. Loren leaves. Twitter for Mac slowly dies. I don't doubt that someone has a rationalization for this, but I have to question the motivations behind such a move. This sounds more like someone trying to get rid of someone else's "legacy", or at a minimum some "new guard" trying to get rid of the "old guard". The Twitter Mac App is well-designed and popular. What good reason could twitter have for killing this?
It sounds like twitter's attempts to "reinvent" itself are going to just push them further into irrelevance.
Of course, if this is just a rumor, then you can pretty much ignore the entirety of my rant.
It's pretty simple why Twitter would discontinue this app. They want to have a consistent user experience across all their clients and they will continue to introduce more rich content (such as Cards) from their brand partners. It's a lot easier for them to manage this consistency of experience by sticking to HTML5 for the client experience rather than maintaining and updating a set of native clients each time newer content features are released.
You know, life would be so much simpler if companies could just force their idea of "consistent user experience" on people. Sometimes we as engineers have to take on additional complexity and just give the fucking customer what they want.
You can give users a rich user experience in a desktop app. Yes it will be more complex. Will it ultimately end in a better overall user experience? It sounds like your stance is "yes", and mine is "no".
It sounds like twitter's attempts to "reinvent" itself are going to just push them further into irrelevance.
Of course, if this is just a rumor, then you can pretty much ignore the entirety of my rant.