It should have nothing to do with when you signed up. Rather it should have everything to do with the year you actually purchase.
It should. Then again, anything's possible these days on planet earth.
I'm late to this party as I never received the Rivian email last week so I've not been given the opportunity to update my agreement. Last week I sent Rivian an email inquiry but they usually don't respond at least for several weeks.
My income is below $150k, our combined income is below...
Based on my limited research, you are allowed to claim one EV tax rebate and your spouse is also able to claim one EV tax credit in same year and at least until tomorrow, you could purchase a new EV every year. IOW, no limit to how many years you participate in an EV purchase.