How much does chatgpt know, if we don't have free will?

If we consider an idea that we don't have free will, and that the factors that effect current events, disease, climate, etc are all based on data that is currently available online, how much could be known with current technology? What does chatgpt not have access to that would limit it's ability to forecast the future?

For example, could chatgpt forecast a change in human language and forecast a slang trend considering it's a language model that constantly updates or is other data required? What is not forecastable with all the known data?

(requires suspending believe in free will if you have it!)