Be careful since you have a BE ticket and the rules on those have changed.

You can always get a full refund when your (original or rebooked) flight is cancelled; it's a DOT regulation and they seem to "enforce" it by fining the carrier if necessary.

When your flight is cancelled, you can normally ask to be rebooked on any DL flight that's reasonable. You don't have to take an early bird flight the next day or a long connection or an RJ segment or anything else you might not prefer if something else is available that's better for you. Sometimes DL will rebook on partners or other carriers with which DL interlines. Otherwise, don't expect DL to reimburse the cost of a second ticket you purchase yourself (vs refunding the first ticket).

If there's a FF reason for wanting to travel in 2021, you can request ORC = original routing credit for what was originally ticketed, provided that DL rebooks the new flights and that they take place as soon as reasonably possible. It won't work if you travel much later or cancel the trip, or buy your own new ticket.