NVIDIA recently unveiled its 2021-2025 roadmap for the datacenter segment. The roadmap indicates that an Ampere successor, likely Lovelace, could arrive next year, with a new GPU architecture beyond that set to arrive before 2024.
https://www.notebookcheck.net/NVIDIA-s-new-datacenter-roadmap-indicates-that-MCM-based-Lovelace-could-arrive-next-year-with-a-successor-before-2024.537375.0.html