Well this would be a big deal/problem if it happened. Via The Points Guy, there’s rumors floating around of Delta switching to a revenue based model for their mileage program. What this means is that you accrue “miles” based on how much you spend on a flight, and when you redeem miles, they essentially convert into a fixed value. Typically this means you will get less value for your miles, and for a non-business traveler, there’s not much you can do to get a great value out of it.
I’m not really a Delta flyer though, but I do have a large stash of Delta miles earned through various transfers and promotions. So if this is at all true, I maybe need to start looking into burning down some Delta miles. Delta Skymiles are already considered a pretty poor value by most people, although there are some redemption options that are gems (Air France to Europe, V Australia).