There are an infinite number of dwarf planets, as we live in an endless void.

Is a dwarf planet a moon?

There are right now only 5 official dwarf planets recognized by the IAU. But there could be dozens or hundreds. Scientists suspect that at least 40 known objects in the solar system will be designated dwarf planets. Estimates are that up to 200 dwarf planets may be found when the entire Kuiper Belt is explored. And there might be as many as 2000 when objects outside the Kuiper belt are considered. A new distinct class of objects called “dwarf planets” was also decided. It was agreed that “planets” and “dwarf planets” are two distinct classes of objects. The first members of the “dwarf planet” category are Ceres, Pluto and 2003 UB313 (temporary name). More “dwarf planets” are expected to be announced by the IAU in the coming months and years. Currently a dozen candidate “dwarf planets” are listed on IAU’s “dwarf planet” watchlist, which keeps changing as new objects are found and the physics of the existing candidates becomes better known. The “dwarf planet” Pluto is recognised as an important proto-type of a new class of trans-Neptunian objects. The IAU will set up a process to name these objects. And where did I get the idea that there may be 12 planets revolving around the Sun? From news, ofcourse. Before the IAU voted on the resolution to redefine what constituted a planet, there were rumors that the new definition would increase the number of planets from 9 to 12. On August 16, 2006, Boston Globe had reported that:

As many universes as many dwarfs and that would be endless!Our knowledge is miniscule, smaller than the Snow White's dwarfs!

truthfully?, well most likely thousands, maybe hundreds, maybe more, we as humans, know very little of what is in fact out there......