The question seems to have evolved a little into 'what will become of this universe eventually'?

IMHO it will always continue to expand and as doing so will run out of heat (energy) and, be so sparsely spread that thinly that darkness will fall across the universe forevermore....

But rest easy this is going to take a very long time.

Understanding the leakage of energy from the hart of black holes does not for me sagest the end of the universe.
Mater can be made to change its form. If pure energy became mater then could the opposite happen ?
If this were so, would it not sagest that the universe will survive for ever.
We just might not recognize it.