What in the world gives you the impression Twitter is in its final days? Naysayers have been saying Twitter fill fail any day now for about 8 or 9 months now.
E.g, despite it being dead since the redesign in 2010, you can still go to digg.com right now, create an account and all. Fark.com still exists. Slashdot still exists. None of these sites are relevant anymore though.