Question: will mercury ever be counted as a dwarf planet?

Iain Bethune answered on 25 Jun 2015:

Mercury is definitely a proper planet, because it has cleared out it’s own orbital path of other sizeable objects, and orbits the sun. It is not at risk of being counted as a Dwarf Planet!

The reason that Pluto was demoted from planet to dwarf (boo!), was that it has not cleared its orbit (in fact it crosses orbits with neptune), and the fact that it is rocky and orbits at an angle to the plane of all the other planets suggest that it was not formed at the same time as the other planets, and perhaps originated elsewhere and was later captured by our solar system