Not sure this exact thing will make it into the next update but
- new Datepicker options are coming (I need a Range Filter - #4 by Daniele), we’ll have to wait and see which ones exactly will be implemented
- if that specific feature doesn’t make it into the next update it’s still possible via JS as shown here (to disable older dates though) Disabling the dates from the past from Datapicker in Pro forms - #2 by manc
If the next update doesn’t provide what you need (since there are so many things to implement), I’d be happy to help you out setting up via JS till the feature comes to BF natively 