I would certainly bet on them going up in the short term. However, going public carries more scrutiny, and that means their two existing problems will be catapulted into the public eye at some point, just as they have been for Facebook:

- political extremism

- very flimsy segregation of NSFW material (and usernames are basically not censored)

I doubt they would be dumb enough to do a Tumblr, but it can't be ruled out entirely.