Airlines are stating publicly that they "understand" how people might want to change their plans - so it's absolutely fine for people to change the date of their flights without paying a change fee - just pay the fare difference (but no refund if the fare is lower). People will tend to panic about not wanting to fly in April - so change their flight to a date in (e.g.) October. Airline now has the right to hold onto your money until October even if the flight in April is cancelled (which it almost certainly will be) and has no obligation to offer any kind of refund
48 hours before your flight in April was due to depart, airline will email all remaining pax to say they can have either a cash refund or a credit note or to change to an alternate date - but the people who have changed their flight to October don't receive this email
All completely legit - the airline hangs onto the money of many pax as a cash reserve / working capital and hopefully stays in business until times are a bit better in October. If the airline goes bankrupt before October, the money has been used to pay things like salaries / airline leases and passenger likely gets nothing from the insolvency process
If as a pax you have a flight booked in the spring, you are best off waiting until 1 or 2 days before the flight is due to depart, and only then should you tell the airline what you want to do