How can i create a column of forecasted dates?

I am working on a solution to forecast dates which are derived from the average of difference between the previous dates.

For example, this data is filtered for plant code, plant and unit. I have calculated the difference in outage dates by calculating the difference between the max date - previous date. The average changes when i change my filters and is a dynamically calculated column.

i want to have a new column which has the forecast dates, the new column should be like the forecast trend-start date column of the below table.
1st row of Forecast Trend-start date column = 10/1/2022 + average of difference in outage dates (result: 12/29/2023)
2nd row onwards = 12/29/2023 + average of difference in outage dates until 2040