Just judging from their past release schedules, it seems like a new version gets released every 1-2 years. 6.5 came out over a year ago now, so I would suspect that 7 should be just around the corner. I would be really surprised if 7 isn’t released at least by next January.
I’ve heard that 7 will feature GREATLY improved rotoscoping tools, as well as 3d text animation improvements, plus who-knows what else. Since Adobe recently acquired macromedia, it’s feasible that they could be trying to better integrate products like Flash, but I’m just taking a wild stab in the dark here. The more new features that they try to cram in, the longer it will take them to release it.
If you have to make a decision on this, I would just say take a look at 6.5, and see if it offers what you need. I understand how you feel about having to make a decision like this, and you of course don’t want to purchase something only to have a new version come out a month later! I have personally never understood why companies like Adobe are so secretive about their products… it just seems like bad business sense to me. It seems like they would want people to know what they are bringing to the table, buildup plenty of anticipation and keep customers from jumping ship to a competing piece of software to get the features they need! But I didn’t take marketing in school, so heck, what do I know?