I doubt that there will be anything as distinct as that. It would not be in dCS’ interest to put out a press release saying e.g. ( just a date at random) Rossini will be replaced by Locatelli in Q3 2022 as they will then not sell a single Rossini unit during the intervening time.
On past experience once the Vivaldi replacement is out then Rossini may be replaced within 12 - 24 months and Bartok anything up to 3 years after that. But dCS may not hold to their previous form of course.
It is just a risk you have to take when purchasing. It isn’t like buying a Japanese TV when you know that its replacement ( and the replacement after that etc.) will reach the shops in June of every year.
There is also an effective “opportunity cost” to holding back. You may decide not to upgrade until Rossini’s replacement is announced and made available. Meanwhile by doing this you may well have lost 2 years listening to what remains a superior product . I have already written here of a childhood friend whose father refused to buy a black and white TV as he knew that colour was coming. So it did - ten years later. So presumably they had no TV for ten years.
My take in any case is that I would tend not to buy from the initial production batch but give it a year to settle down and for the major bugs in the field to be discovered; sceptical or just realistic?