As far as industry rumors go, I'm going to file this one under "I don't want to see it happen, which means it probably will". I've been reading all sorts of things on this, one constant being that it's expected Dungeon Runners will be shut down, with a few sprinklings of a potential TR closure this time next year if the game doesn't see more subscriber revenue.
With Dungeon Runners, the closure would be a surprise to me if it does happen anytime soon. From what I've seen they've got a solid retail presence, being on the shelves of just about any major retailer who sells PC games in my area. Pulling the plug on a title just after securing shelf space tends to come off as a slap in the face to your retail partners, not to mention anyone who just purchased the box copy. You know, the old bait-n-switch routine ala the pre-order boxes for GnH.
Hopefully something official is announced by NCSoft soon, but as it goes when there's not an immediate PR statement to deny the rumors that by now are posted at most gaming sites it does tend to lend a certain amount of credibility to them.