The evidence is already all around us that NSs readily pronounce 2010 as twenty ten. This is a change, given that the year just ended was two thousand (and) nine (BrE with and, AmE I think without).
You can see that *twenty nine would not have been a possible way of saying 2009, since it would be heard as 29. But why not twenty oh nine or even twenty hundred (and) nine?
My father was born in 1909, which we call nineteen oh nine (at least, that’s what I call it). But my mother was born one year later, in nineteen ten.
On a related topic, let me record for posterity the following small linguistic change from the first half of the twentieth century. If you asked them the time and it was 11:25, my parents would both have said five-and-twenty past eleven. But like everyone else nowadays (I think), I have always said twenty-five past.
This was the only context in which they would use the old Germanic formula x-and-twenty, apart from in the nursery rhyme where we all do.
Sing a song of sixpence, a pocket full of rye;
Four-and-twenty blackbirds baked in a pie.
When the pie was opened, the birds began to sing;
Now wasn’t that a dainty dish to set before a king?
For the young, and even now the early-middle-aged, sixpence ˈsɪkspəns belongs to Britain’s pre-decimalization currency. From 1971 it became 2½p. Now, after the demise of the half-p, it is no longer expressible as a precise sum of money that you can handle.