Tim Beiko confirmed that Ethereum upgrades would follow the PFI → CFI → SFI framework, where proposals move through stages of consideration before final inclusion

Quotes that support claims

The existing PFI → CFI → SFI framework remains applicable here. Counterintuitively, our technical bar for CFI/SFI status on flagship features may be lower than for regular EIPs, but only if they strongly align with the chosen Fork Focus and enjoy robust community support. Some features (e.g., The Merge) are critical enough to justify an all-in effort despite imperfect initial specifications. Others, such as EOF, may be presented as a set of EIPs, or even non-Core EIPs, like for those related to the gas limit.