If we could thrawl space for dissipated matter and energy and thus create new stars, wouldn't the stop the heat death?
That particular method won't work, since stars "burn" fuel and eventually all will be gone. However, combining general relativity with quantum physics might allow us to control the shape of spacetime in a way that basically amounts to creating new "baby" universes.
Alternatively, an expanding universe can not actually experience heat death, since the expansion itself causes the ambient temperature to fall. However, taking advantage of this fact would require giving up anything resembling our current fleshy forms. Of course, we'll probably end up doing that anyway, since mind uploading has obvious advantages once we leave the only known environment - Earth - where our bodies are actually convenient. And of course, it might turn out mind uploading is actually impossible, in which case we have problems.
And of course, it's always possible that the Laws of Thermodynamics are not, in fact, absolute, or more likely, don't mean what we think they mean. It wouldn't be the first time people jumped to conclusions without thinking of all the implications.