Surviving is a pretty bad metric, especially for social media. Digg "survived". So did MySpace, Tumblr, and more. It's too soon to say about Twitter, but their future (in general) doesn't look very bright. They aren't going to disappear, but they also aren't going to be the cultural powerhouse they used to be.
More importantly, the move needs to be profitable. On the surface, it is- 3rd party app users don't currently bring in money. Converting any of them at all to paid or ad-viewing users yields a net profit, if you keep a narrow focus.
Having these users active and engaged on your platform has a value as well, but one that's really hard to quantify.