Given the horrendous political advice that the Romney campaign appears to be listening to internally, I have a feeling they will release the tax returns right before the Olympics or while Romney is already in London. They will hope the two weeks of the Olympics will insulate the campaign from questions. Basically, when Romney starts campaigning again the canned response will be, we already addressed this. Except they will never address it. They just want the Olympics to wash away any potential questions.
This is not the advice I would give, but it seems par for the course with these fools. They are running a textbook campaign of what not to do. Why stop now?