It is no secret that Manhattan's Serendipity will open an outpost sometime this year/early next on the corner of Wisconsin and M, in the old Nathan's space. I think the trademark larger-than-life frozen hot chocolate sounds like a great antidote to the nasty July and August DC heat.
Future Home of Serendipity DC
But it also appears a West Coast transplant is soon coming to M Street too, with a Sprinkles location set to open in January a bit further down the block. Direct cupcake competition!