There is a case to be made that the universe . . . or universes . . . is / are eternal !
It (they) will undoubtedly rearrange itself (themselves) but matter won't just disappear . . . it's here to stay, in one form or other !
It's the opposite of nothingness . . . as long as one is there . . . so will the other !
Nothingness won't ever disappear either !