I don't know what the future holds for it. Trimble has said that they are committed to the free version of SketchUp so at this point I wouldn't worry about it. If you don't have the most recent version of SketchUp 8, you should get it anyway. That's just so you have the most current version with bug fixes and so on. Go to Help>Check for updates to see how you're sitting. I've read of some people thinking about jumping ship now. They seem to think that Trimble will do away with the free version some day. To me that's like saying they won't use their drill press because the model has been discontinued and the manufacturer is no longer selling it. One guy wrote that he'd download and had been thinking of learning SketchUp but now he won't because of this change. He's just shorting himself. Even if there never will be another free version of SketchUp (and I'm not saying that at all) SketchUp 8 will do anything that a woodworker needs and more. I don't even use it to its fullest capacity.
So the upshot is, just keep using what you've got. Keep it current with maintenance releases when they come and don't worry.