I see no benefit of getting a CC or doing a mattress run because based on the articles below you will receive all of your usual benefits. Lifetime annual count, 50 nights and 75 nights gifts. So unless you are looking to racking up bunch of points by receiving your CC sign up bonus then little benefits of getting the CC.
Didn't you get an extension of your status through end of February 2022? I believe Marriott extended everybody's status for an additional year. Additionally, recently they announced that they will deposit 50% elite nights based on your last year status into your account by end of July. I believe you should be set for 2021 either way. However, 2022 most likely will be business as usual and has to be earned in 2021.
Here is an article from Points Guy website regarding extension of benefits:
https://thepointsguy.com/news/marrio...e%20in%202020.
Here is an article about 50% elite night credits from Point Guy:
https://thepointsguy.com/news/marrio...edits-posting/