Taso, you have been lucky. Almost all of mine are scheduling for 2021, not 2020. They are moving to 2021 for lots of reasons, not all by choice. I know some venues not even allowing to rebook for 2020, which makes no sense but none the less, most are rebooking for 2021.
Are you saying that most of your events booked for 2020 are booked by March-- meaning you take no more business at your max number of events, which has almost already happened for you? I typically book all the way tough October, even for the current year as that is when the holiday and corporate stuff begins to book. (that's when I reach my max number of events). If so, that's amazing, and kina crazy!
If my clients moved their date to this 2020, it would only be a small hit as I am still giving up fall and winter dates, but still giving up plenty of dates, and you're not?