If AMD wants to go beyond single digit share in consumer GPUs, they need to invest into their software support. This means at least ~7 years of mainline support for the desktop GPUs and ~5 years of mainline support for mobile GPUs.
For RNDA1 this would mean it would be fair to sunset mobile support in late 2025 (last RNDA1 mobile GPU was the Radeon Pro 5600M released in Jun 2020). For desktop dGPUs, that would mean a support window until August 2027 (the last RDNA1 dGPU released was the Radeon Pro 5300 in August 2020).
For RDNA2 this would mean both mobile and desktop support till 2030. If AMD doesn't want to extend RDNA2 support, then don't release products with RDNA2 in 2025 (mobile) and 2023 (desktop).
Honestly, I can sort of understand moving RDNA1 to maintenance mode by say 2026Q1. RDNA2? They literally released a mobile RDNA2 product a few months ago.