It's not everyday that someone asks my opinion on the 'metabolic'. You're kind of catching me off guard here, but I'll give you my gut reaction. I understand metabolism as a creative-destructive duality that releases energy. The key element of the concept (for me at least) is that both a creative act and a destructive act work equally in tandem. My first thought regarding two universes colliding is that it is more of an accident rather than a creative-destructive occurrance. You're thinking/question is not to be discounted, however, because this new 'beginning of the universe' theory may well represent an important point of distinction relative to the metabolic process, ie, an interesting place to figure out what can be deemed metabolic and what cannot be thus deemed.
I see my painting on the Gehry chair as a metabolic act because while I was being artistically creative I was at the same time being destructive. The chair is still a chair, and even still a Gehry chair, yet it now also a unique work of art by Steve Lauf, namely Museumpeace. The creative-destuctive process is now integral to the piece, as is the notion of duality, and creative-destructive and duality are the operative concepts that (I see) must be present. Now I could take this example further and ask whether Museumpeace has an energy that wasn't there before. Personally, I think there is an energy there that wasn't there before, and hopefully that energy is getting a little stronger every day.