Hmm... that picture looks like it would be a grand queue to me. Who knows what they have in store, but I think a brief glimpse of the interior prior to entering Diagon would be a must.
On another note... Leaky has no 1st floor windows on Diagon correct? So, is it possible the first 15 feet of the interior space that parallels Diagon will be for Hogsmeade style shallow storefronts and the interior nothing but a stone wall?
And might I add, HTF is not answering my question regarding Grimmauld a page back.... hmmmm.