Where can I find data on past forecasts of planned aircraft production?
Yes both Airbus and Boeing deliver 20-year forecast for the complete market. For Airbus there is a spreadsheet which may function as your database.

IATA also publishes 20 year travel forecasts, here is the latest. Airline travel is going to double over the next 20 years.

At he time of first production, forecasts for the aircraft are made based on market forecasts, plus the expected market share that the aircraft may achieve. Information that is of interest to the stakeholders of the company.