From Carl Sagan's Cosmos;
Another similar philosophical saying;
It is an interesting conjecture, but obviously cannot be proved. If our universe is apart of a multiverse, there is no reason to claim that the multiverse isn't apart of some greater multiverse, and so on forever. And who knows, perhaps elementery particles can become infinitely small (correct me if this has been proven wrong). So in a way the closed electron universe conjecture isn't all that different in essence. An infinite regression up and down is what they both (this conjecture and M-Theory) share. Both also have an equal amount of physical evidence (unless you consider mathematics as physical evidence ;)).
BTW though, why does it have to be a closed electron as opposed to a closed proton or closed neutron? Is there some universe manifesting property suspected in electrons?