I have to be honest and admit that I had a similar thought when I read the last chapter of Destiny. It seemed like the perfect ending not only for the novels but for Trek itself. The Federation's greatest enemy was destroyed not by force but by the ideals upon which the Federation was founded. While the Federation and its allies are hurt, they are still strong and they are coming together more and more. It just seemed like the perfect ending to me.
But Star Trek
isn't about defeating enemies. It's about exploring the universe and the human potential. The defeat of the Borg isn't the end of the story, it's the beginning of a new phase, a new situation to be explored.
That wasn't actually what I meant by what I posted (that it was over because they defeated their greatest enemy). To me the last chapters of Destiny were what Trek was all about, sticking to your ideals and exploring what it means to be human. The Federation stuck to what it was founded upon and a new era is upon them - the undiscovered country to borrow a phrase. The small gathering between Crusher, Dax, Picard, Riker, and Troi was a perfect ending for the 24th Century Trek series in my opinion.
But, as I also said, I doubt that I'll stop reading. It was a momentary thought (to be honest I picked up both Myriad Universes collections this evening and I'm already starting on The Chimes at Midnight).