China has extended most visas additional 60 days

No, once the 60 days are going to expire, you should extend you visa at the local exit and entry administration for a 30-day stay.

Once the 30 day grace period has ended, can it be renewed for additional 30 day in perpetuity so long as travel ban is in effect?

Thank you.

If the travel ban is still in effect, you may get bthe additional 30 days. However, if there are flights back home at that time, you may not get the extra 30 days.

If you have a tourist visa that will expire, they wont extend it or issue a new tourist visa. Even if your current visa is for 10 years, once your 120 day stay (or whatever amount it is) runs out, they will cancel it. There are currently fights leaving China.

Also worth noting, if you are eligible for an extension, you will likely be required to have a full body medical check before you can even apply.