It'll be quieter "I'm not running again!" announcements within the Party, rather than more publicized retirements. But I imagine quite a fair few, because of this:
Biden is already a lame duck, and if today's developments (along with the developments of all of October, really) are anything to go by, nothing on the Democratic agenda will be accomplished during the Biden administration, unless some god-tier politicking somehow saves the day. Next November they are pretty sure to lose their majorities across Congress and then they'll be out of control of the legislature. A Republican Congress wouldn't get much done either, sure, but they could just blame Biden for stonewalling them. Or Harris, depends on Biden's health.
And then in 2024 Trump will be back and with 4 years of Democrats have accomplished zilch in power, as well as with the economic situation of Americans probably in a very sorry state even compared to the beginning of 2021, he's almost certainly going to be back in the White House. And when that happens he'll be back with his Congress controlled by his party, which will be much more loyal than it was the first time. If they couldn't even fortify Virginia, how will they fortify the nation?
And then who knows? Even if Trump did absolutely nothing and the public magically forgot the woes of the Biden admin and Democrats got back control of Congress, that'd be taking place in 2026. That's a long ass time. And I'm not even getting into what will happen within the Democratic Party in that time because who the fuck knows.