Will the Universe Run Out Of Energy?

Thanks Fraser for mentioning my name at the end of one of the more uplifting videos, that's something I won't soon forget. Anyway, here's a thought. What happens to Dark Energy as the Universe cools down? With everything being stripped down to its virtual atomic structures won't Dark Energy actually stop the Universe from expanding since so little energy is left and if so(Hope!) somehow, someway cause an equally long implosion of particles back to their origins so that another singularity is created and, voila, another Big Bang thereby the cycle begins once again? Just a thought. Love the videos (hey, a dog's gotta do what a dog's gotta do).