Problem is when the Doctor saw the Woman in The End of Time he recognized her, but when he met Clara in The Snowmen he didn't recognize her. Which kind of rules out they could be the same. Really doesn't make a whole lot of sense that in The End of Time the Doctor could remember that random girl who lifetimes earlier told him which TARDIS to steal and then forgot all about her years later in The Snowmen.
Its similar to the speculation that David Tennant's character in the 50th could be the metacrisis Doctor... which it wont be, in fact we should never speak the word 'metacrisis' again... ever.
Definitely not the metacrisis Doctor in the 50th since photos show Tennant wearing the brown suit.