Oh, yeah! I didn't mean advance filming, just pre-production. Fairly conceivable that they'd be doing regular casting around now, and the new Doctor's going to be a much heavier duty operation that needs to be done for pretty much the same deadline. Especially if they do something timey wimey, which... I'd imagine Steven Moffat would like to if he can. Particularly in the anniversary year, coming straight off the anniversary special. They won't if they can't, and if MS's departure has snuck up on them then yeah, not a snowflake's chance in hell.
Don't get me wrong, I do think it's incredibly unlikely we'll have a name tomorrow... I'm just quite enjoying the possibility. As rumours go, it's not built from the "Simon Cowell to play Davros" mould.