I believe that this post is the most recent announcement related to this: Forge pricing update: free through 2023
The direct answer to your question is near the end:
What happens after December 2023?
In the spirit of Atlassian’s OCNB value , we still need more data on Forge app usage to determine a long-term economic model. Our preference is to keep Forge as free as we can: we see its primary value in improving Atlassian products to better serve every customer. In any case, we will always remain competitive against the platform costs and benefits of cloud providers. We will share an update on the long-term plan by September 2022 at the latest, though we endeavor to do so significantly earlier if possible.