The Montgomery County coordinator told me last week that in general, the majority of spots will be accepted (and wait list positions offered) by the end of the school year (early June).
However he said if you are taking a long trip over the summer make sure they have your cell number (and not your home number) on file if they need to get in touch w/ you. The letter you got in April, telling you they received your application, should show the contact info they have for you.
I know a few people offered spots over the summer last year... One neighbor (whose child was wait listed at #7 in a French program) was contacted in mid-June.