The Witcher 4 release date may not be as far away as you think. CD Projekt Red has built a reputation with some for taking a long time to develop games and revealing them very early, but neither of these beliefs are based in much. Cyberpunk 2077 was announced eight years before it released. If this is your only reference point, it's easy to think CD Projekt Red announces their games way ahead of release. However, Cyberpunk 2077 is a one-off for the Polish developer. CD Projekt Red announced both The Witcher 2 and The Witcher 3 two years before they released, which of course is more representative of your standard AAA release.
Cyberpunk 2077 also gives players the impression that CD Projekt Red takes a long time to develop a game, but again it's misleading. While Cyberpunk 2077 was announced in 2012, it didn't enter pre-production until halfway through 2016, with proper development with a properly sized team beginning even later. Meanwhile, The Witcher 3 was made in roughly three and half years while The Witcher 2 was made in a similar amount of time.
What does this have to do with The Witcher 4? Well, this week CD Projekt Red announced it will begin the development of new Cyberpunk and Witcher games starting in 2022. If this is the case, it would presumably mean The Witcher 4 -- or whatever the project ends up being called -- will be out in 2025 or 2026 given the aforementioned timetables. Working backwards, this would suggest the game will be revealed sometime in 2023 or 2024 if it's going to have a similar reveal-to-release schedule as previous entries.
What we know is it won't have is a huge gap between reveal and release like Cyberpunk 2077, because this week CD Projekt Red also confirmed it wants to shorten its approach in this regard, or in other words, reveal its games when they are closer to release.
For now, take all of this speculation with a grain of salt because that's all it is, speculation. However, it's not completely unfounded speculation, and after Cyberpunk 2077, CD Projekt Red is probably itching to move on and get back to its bread and butter.