What makes you think a return will be required for 2021?  Are there carryover capital losses that you want to distribute to the heirs?  Probably not much in "excess deductions on termination," which probably won't be deductible anyway.  

IRS doesn't keep track of these things.  I just got a call from a client for whom we filed a "Final" 1041 for 2019.  He just received 1041-ES payment forms to use in 2021.