I don't count Mikaela as a significant enough plot device.
The planetary structure itself was seen collapsing in on itself, but I guess without someone actually saying so in the movie itself, anything is possible later as an explanation as to why it survived.
(we already saw a large portion sheered off when the portal was closed the first time - so I guess the writers didn't want a big slice of metallic planet left sitting next to Earth at the end of the movie as a loose end)