Is there much added benefit to upgrading to a disc wheel from a rear areo wheel?

There are many average cyclist out there that want to get faster but focus on the gear rather that the hard work.

Is there a athletic level or average speed that would warrant the upgrade?

I currently have a Zipp 404 rear and average 22-23 mph in most olys. 21-22 in half-im's.

If my training continues to improve would I also benefit from the addtion of a Renn Disc?

Thanks