Hold off on making changes or cancelling. Your travel is not until July & September. Schedules will not likely be fixed until June & August respectively.

If DL cancels your flight, you are entitled to a full refund to your original form of payment, e.g. credit card. If you cancel under a COVID-19 waiver, all you get is a credit for future use. You may find that you don't want to travel, that DL doesn't serve the route you want or that there are better schedules at better prices on other carriers. Thus, having cash means that the choice is yours.

Forget about DL (or other carriers) notifying you of cancellations and changes. It is really on you these days to confirm what is and is not the case and you clearly have that capacity.

The fact that your flight is not bookable right now means little. It could be on the chopping block or DL may be considering other options, including a smaller aircraft.

But, you gain nothing from cancelling early.