Something from the 70s works perfectly fine, except it can't run on anything bare any longer, and the hard drives etc. have all long since failed or their PSU capacitors have blown....so Twitter will absolutely rot, how fast depends on several factors.

I personally suspect the infrastructure used to build Twitter will rot faster than Twitter itself, and of course the largest most dramatic source of rot is the power required to run it - several large communities have abandoned it already, making it less much less relevant, meaning the funding for it will also dry up, meaning more wasted cpu cycles and the like.

Thats of course assuming its left in some sort of limbo, it doesnt sound like thats the case with the current management, its only a matter of time before it topples over from shitty low-rate contractor code. Honestly, the app worked like so much hot garbage already, I could see it falling over itself and imploding with a couple poorly placed loops...