@Inna22 That's a pretty interesting proposal. My only concern would be that you might be blocking dates that someone else could potentially be wanting to book. But on the other hand, it's not really any different than what our airline did with us this summer, when they cancelled our tickets but then told us that we could book the same dates next year.
I guess that it's really a judgement call. Do you get a good feeling about these particular guests? Do they seem like they genuinely like your listing and are sincerely interested in staying at your place next year? If so, then giving them that reservation might be considered a nice act of good faith on your part, which could potentially lead to a positive review from them down the road.
Would love to hear what you decided in the end.