I doubt even Ryanair knows at this stage as it varies from year to year and base to base. E.g. a new base from March/April like Leeds is already bookable for early summer. Where they still have a lot of winter seats to fill they will release the summer timetables later. If you do not have to fly on Fridays and Sundays, however, you are better off waiting until they start flogging off the seats at £10 or less.