While Rev 5.0 V1.0 is the current standard, the industry is already discussing M.2 for PCIe 6.0. However, the 1.0 version of the Gen5 spec includes forward-thinking notes:
Technologies. PCI™ Conventional. PCI Express® Base. PCI Express CEM. PCI Express Cable. OcuLink. Copper External. Copper Internal. PCI Express M.2 Spec Rev5.0 Ver1.0 0429202 NCB - Scribd pci express m.2 specification revision 5.0 version 1.0 pdf
The higher current allowance for 3.3V accommodates PCIe 5.0 controllers (e.g., enterprise NVMe SSDs) with increased logic and signal conditioning circuitry. While Rev 5