It comes down to whether you want to go or not. It’s certainly not out of the cards at all that Disney would be open in July (personally, I’d be surprised if it wasn’t open). Unfortunately, nobody really knows when it will reopen and what that looks like. The benefit of keeping your reservation is that you have a reservation and can go if the parks are open. If you’d otherwise go if it were open, then keep the reservation and plan on going. But if even if it is open and you’re not sure you’d enjoy going for the time being, then go ahead and cancel. The benefit in that case is that you get your money back and can stop worrying about it.
Also, keep in mind, Disney is currently not waiving any cancellation or modification fees for packages with arrivals after June 30 (obviously this could change), so if you have a package booked, you’d want to make sure you cancel before the 30 day mark from your arrival, provided they haven’t extended that window or given any more information about a reopening. This doesn’t matter if it’s a room only reservation.
Finally, even if you cancel and the parks stay closed, I’m fairly confident that Disney would include you in any sort of guest recovery offer they put out should they decide to offer one in that scenario. There’s, of course, no guarantee they’d offer some sort of recovery offer, but those who were included in the recent free dining offer were both folks who had their trips cancelled by Disney and folks who canceled themselves after the park closure announcement. Again, that’s all speculation. Disney’s own indications seem to be pointing toward a June opening, so it could all be a moot point but this remains a very fluid situation.
I know it’s the answer none of us like to hear when asking for advice but, as they say, it’s a personal decision.