California taxes capital gains at 13%, and 9 states have none (Alaska, Florida, Nevada, New Hampshire, South Dakota, Tennessee, Texas, Washington, and Wyoming). As an employee, you could save $130,000 on your $1 million dollar gain.
That pays for an awesome rental house in Seattle or the Nevada side of Lake Tahoe. It will be a lot more tempting since you can just ride out covid for a year or so and keep working remotely like you are now. You can time this to your liking since the trigger is you selling the stock, so you can move in 2021 and sell in 2022. Realistically having 1 successful IPO is very lucky, maximizing the return makes a lot of sense.
And I think this is much a much sharper decision than for public company employees. You will have been accumulating stock for 4-10 years and it's been completely illiquid. You get this big hammer of a tax bill when you sell, and it's very tempting to optimize it. This is always happened a little but in covid times, it seems like it will be 10x of the usual. Expect a lot of complaints from Seattle and Austin :-).