Syncthing will soon be releasing v2.0.0 (it currently has a release candidate). There are major changes that users should be aware of. In particular, the database backend is switching from levelDB to SQLite. On the first launch of 2.0.0, there is a migration which can be lengthy for larger setups. This is normal and should only happen the first time this version is launched.
We're waiting until the final 2.0.0 release is out (no ETAs) to upgrade the package in unstable. I'll update this post when that happens.
When we upgrade Syncthing to 2.0.0 in the stable repo, we'll include it in the weekly sync notes.
The full change logs are here.