The GitLab migration was never about changing how bugs are reported. The bug tracker is still The Place for bugs. Salsa (the name of the GitLab instance) is just voluntary infrastructure for git, replacing the previous (also voluntary to use) Alioth service.

There are some attached hooks that automate some Salsa-BTS interactions. For example, making a commit that references closing a bug will automatically send a message to the BTS letting the reporter and others know that a fix has been committed. The bug will actually close only when the new package version is in the archive (the archive is still fully git-oblivious).

That said, the Salsa migration is complete, and Alioth is no more.

Is it planned to move issue tracking to Salsa?

I enjoy filing bugs via email, because that does not require me to create an account and I need email notifications to become aware of updates anyway.