Well, there seems to be a consensus (among astronomers at least) that Pluto is only considered a planet by historical accident. Nobody really wants to "demote" Pluto, but that doesn't mean that other KBOs will be considered planets. Of course, "tenth planet" has such a sensational cachet to it that the phrase is adored by sensationalists (which includes many, if not most, journalists)...

The trick, of course, is that "planet" is not really defined, so we don't know whether size should be the only factor, or whether composition or orbital characteristics are significant too. Composition is already a messy business, with at least two types of planets (rocky planets and gas giants); Pluto and other large KBOs seem to be not so rocky and more just icy, so maybe they're just supercomets. It's all rather a disorganized, ad-hoc mess. :)