If you get rid of the 140 character limit, wouldn't twitter just be livejournal? On livejournal, you had the ability to friend people, and all of their posts would show up on one page. Friending didn't have to be reciprocal on livejournal, which is the only apparent difference between facebook and twitter. Or really, how is twitter different than an email list that anyone can subscribe to?
When twitter was first launching, it seemed to basically be a text message equivalent of an email list. Once people started getting smartphones, I assumed that there would be no reason to use twitter. I'm assuming that twitter is just costing on momentum caused by someone deciding it was cool, and that it's dying.
Alternatively, I'm shaking my fist yelling at the kids to get off my lawn, I'm not sure.