The final forecast is issued when 538 stops updating this page: 

https://projects.fivethirtyeight.com/2022-election-forecast/senate/

Nobody outperforms if the forecast is in between the modal outcome (highest %) in the "How many Senate seats we expect each party to win" bar graph and the "Average seats controlled by party" line chart.

For example, at time of the creation of this prediction, the modal outcome on the bar graph is a 16.2% chance of 51 R seats, and the average seats line chart is at 51 R seats, so if the final outcome is 51, then Fivey wins.