I should think so. According to
dell.com/amex -- "
More value from Dell in 2020: Get up to $100 in additional statement credits from May 1 through June 30, 2020 and up to $100 in additional statement credits between July 1 and December 31, 2020 on new U.S. purchases with Dell." It doesn't distinguish between new and older accounts.
I'll probably be testing this within the next week.
Seth