ADuck
Legend
For fun I'm going to try to use Federer's age as the main predictor.
Federer:
Slam winning form range: 2003-2019 (17 years)
Age of last slam-winning form year: 37-38 years old
Nadal:
Current slam-winning form range: 2005-2022 (18 years)
Current age of last slam-winning form year: 35-36 years old
Age predicted last slam year: 2024 (Will be same age as Federer)
Age-range predicted last slam year: 2021 (Exceeded Federer's range)
Djokovic:
Current slam winning form range: 2008-2023 (16 years)
Current age of last slam-winning form year: 35-36 years old
Age predicted last slam year: 2025 (if age cannot exceed Federer)
Age-range predicted last slam year: 2024-2025 (If range cannot exceed Nadal or Federer's)
Federer:
Slam winning form range: 2003-2019 (17 years)
Age of last slam-winning form year: 37-38 years old
Nadal:
Current slam-winning form range: 2005-2022 (18 years)
Current age of last slam-winning form year: 35-36 years old
Age predicted last slam year: 2024 (Will be same age as Federer)
Age-range predicted last slam year: 2021 (Exceeded Federer's range)
Djokovic:
Current slam winning form range: 2008-2023 (16 years)
Current age of last slam-winning form year: 35-36 years old
Age predicted last slam year: 2025 (if age cannot exceed Federer)
Age-range predicted last slam year: 2024-2025 (If range cannot exceed Nadal or Federer's)