The intention is certainly not that it would return $4M p.a. with the current size - only that it would eventually grow to a size where that is practical. Many proposals have pegged that around the $100MM mark.
The DAO is definitely not intending to time trades, or hire anyone who does! The goal is to average out of ETH exposure as much as possible, modulo our unearned income.
There’s a good discussion to be had about whether unearned income should be denominated in USDC or ETH. We could definitely change our accounting basis to USDC, though it runs the risk that we end taking paper losses if the rate changes between a registration happening and the ETH being converted.
That is definitely the goal of the endowment, agreed.