I would not hold my breath waiting for an answer from Atlassian. This is a highly sensitive topic. But there are some public pointers that showcase the future of Connect.
The first is the announcement of Unifying Atlassian Connect and Forge. That announcement caused such a scare that Atlassian had to write an update. However, the update is still clear on the endgame:
We heard some developers express concern that Connect will be removed from service in 2022. We want to be clear: this is not the case, and we apologize for the ambiguity. The end of 2022 is the date when we expect that all apps will be able to start the process of going from State 1 to State 2 (and many will be able to start the process sooner). It is not a deadline for making the updates necessary to move to State 2, nor is it the date when any Connect services will be switched off.
In the spirit of OCNB, we do want to be transparent that remote iframes and JWT auth will be deprecated in Connect at a future date. We don’t yet know when the official deprecation date will be for these Connect features, but we are committed to providing equivalent functionality in Forge and plenty of time to make updates before any Connect functionality is removed. We know replacing these features is likely to be a significant undertaking for Connect app publishers, and because of this, we decided to provide this information early, even though the pathway to reaching State 2 is still being built.
If you use JWT and remote iframes in your Connect app, we ask you to collaborate with us, keep providing your honest feedback, and share the details of your implementation. Our priority is helping Partners get to State 2 with as little disruption as possible, and to do this, we need to understand your current architecture. This will inform both what we build for you and when.
The second giveaway is that Atlassian is deprecating Connect features and is replacing them with Forge-only support. For instance, see Deprecation of Connect JS getSelectedText API for security reasons
Finally, new features and products will only support Forge. This is true for extensibility of Automation for Jira and for Compass (see https://go.atlassian.com/compass-developer)