I upgraded to a full suspension MTB this year because I wanted it and I had the cash...that said, my old MTB was perfectly good (gave it to my grandson) and my hybrid with a set of wider tires would have sufficed (in fact the Frankenscwhinn with 38 tires was what I started Trail riding on)...one fellow in our group rides his folder/hybrid with 28 tires. If you stay off the more advanced/technical trails, you may find your current bike is up to the task...at least until you see if you like it.
Obtw, the shops around here RENT MTBs...if your LBSs do as well, it is a great way to try out different models over a day or a weekend. I rented a high end road bike when I was trying to decide on a new one a couple of years ago. A great way to get one out and get away from the salesperson.