Do we say "two thousand ten" or "two thousand and ten" or "twenty ten"?
I'm convinced the answer will be 'twenty ten'. It takes an extra syllable to say "two thousand ten". Does an extra syllable matter? You bet.
English has a pattern of simplifying speech. We can determine much about how English was pronounced 500 or 1000 years ago by looking at misspelled words or contractions.
From misspellings in letters from the barely literate we can understand what changes in pronunciation happened over time. For example, when you see a word like "gonna" you can assume it reflects a common simplified pronounciation of "going to". And it's only one less syllable.
We will probably start referring to years like 2006 as "oh six" when used by itself. When describing a range of years like 2006 to 2013 we will say "two thousand six to two thousand 13" for consistency. It rolls off the tongue easier.
I will post more information about the history of English later in twenty ten.