I believe this is just the way you described. Elementary particle physicists have predicted that matter doesn't exist when we are dealing with extremely high (condensed) energies. This is supposed to happen inside the black holes, for instance. I mean right beside the singularity. but even before we lose matter and gravity (!), we shall get reed of strong and weak nuclear forces and electromagnetizm. These three will play dead first, if I'm not mistaken. particles responsible for the first two interactions will disappear (turning into another forms of energies), etc... We will end up with Higgs field/particles... Well, it goes too deep into cosmology, becides, I'm not an expert. Take care!