Will Uefy 2.0 support my older metarigs?

Yes and No

Rigify has been around for a long time and many of the rig samples (parts) are now deprecated. Uefy 2.0 is designed around the modern metarig as it is meant to be used in Blender 2.83 LTS and above.

In most cases a few adjustments to older metarigs options will make them compatible. But you must edit the metarig samples to update them as necessary.