If it would help keep his buddies the rats in office next election, Putin might be willing to just put on a show to make Biden look good and then at least appear to back down for power behind the scenes. Or, he might feel regaining Ukraine is worth having to face Trump in the future. A bird in the hand being worth more than two still in the bushes....
If Putin is serious about regaining Ukraine, my guess is that he would annex eastern part of the country.
The government in Kiev would survive but the country would be much smaller.
USA would launch sanctions against Russia but that's about it. EU won't do anything because Germany depends on Russia for natural gas. They can shut off the pipeline then Germany will freeze in the middle of the winter.
Trump will win easily in 2024. Putin has to decide if that's worth it. Plus the possibility of guerilla warfare in Ukraine.