That’s the beauty of McNeel’s business model. Other products charge maintenance and you basically pay for new releases sight unseen. But with Rhino, you decide if you want what the new release has to offer, and you are free to pass if you don’t feel it has value for what you do.
I will say this though. I manage Rhino at a company with around 140 Rhino users here in Canada and another 30 or so in the US and Mexico. I lost count of how many of our users commented on how much they liked V7 more than V6. If you can upgrade at a student discount and you can afford it, you might want to give it a second thought. Remember, owning V7 will also entitle you to work with the V8 WIP. You may find something there that appeals to you.