New C++ based exporter has existed since 3.1, importer since 3.2, and both have been marked as non-experimental since 3.3 (the python one was marked as legacy since 3.3). The new I/O OBJ code is both many times faster, and has more features (vertex color attributes for import/export, multi-file import).

So this removes the Python based addon. Together with this change, the io_scene_obj folder from blender-addons repository should be removed, which is bulk of the code (~2500 lines).

So far I did not hear many opinions whether it's important to keep backwards compatibility with the old addon. Only Bastien expressed an opinion that backwards compat should not be attempted, i.e. any operators are not official API to begin with, and even more so for operator functions coming from an addon. This blurb has been in 3.3 release notes already:

The Python based OBJ importer/exporter is marked as "legacy" in the menu item now; the new C++ based one got "experimental" label removed. Addons using bpy.ops.import_scene.obj and bpy.ops.export_scene.obj APIs are strongly encouraged to switch to bpy.ops.wm.obj_import and bpy.ops.wm.obj_export.

Together with the addon removal, this also removes Python OBJ addon tests. The C++ based OBJ I/O has way more extensive tests as part of gtests suite.