On the all core devs call just now @holiman proposed an “EIP-centric” upgrade process rather than a hard-fork centric model like we have now. @AlexeyAkhunov also expressed concern about a deadline, like the May 17 Istanbul deadline, meaning that folks would have to rush their EIPs in before the deadline lest they “miss the boat” and have to wait 9 or 12 months until the next hard fork. I’m also concerned about people submitting half-baked “placeholder” EIPs before the deadline.
I like Martin’s idea a lot, especially in combination with smaller, more frequent hard forks. @shemnon’s proposal at https://github.com/shemnon/EIPs/blob/4e3069b4f9a30a639b142151dc6295f634712786/EIPS/eip-network_upgrade_windows.md looks reasonable to me.