I had Broadway tix in early April, they were refunded the day after the show was cancelled. I'm not sure they realized then what was coming, it was more like, "sorry your show was cancelled, good luck finding tickets for a future performance!" Concerts have been a pain but when they have been postponed they give you 30 days to request a refund, and when they've been cancelled they are automatic (if slow). Some are still "indefinitely" postponed which allows them to sit on your money longer.
I also have MLS season tickets and took the refund over the credit, even though the latter came with some bonuses. I still don't really believe there will be a normal 2021 season, at least not on time. I will still be required to renew and start paying for those in the fall, however (except I probably will give the tickets up).
I took the credits from the airline too (for two flights in March) but am tempted to request a refund if possible. You should totally ask for a refund, given the destination isn't being served, that opens a window for you that might not otherwise exist. I'm just assuming the expiration dates on the credits will continue to be pushed forward.