That stinks. I had enough for two award tickets at 15,000 each. Now at 20,000 miles, I only have enough for one.
If you are flying mostly mid-range hops, say DEN-LAS, which is my primary flight, you now need 20,000 / 629 = 32 segments to get a free ticket. Over at Southwest, you only need 16 segments for a free ticket. So, Early Returns may be "one of the lowest" but it is not "THE lowest" in terms of number of miles needed for a free ticket.
Also, Southwest isn't changing the rules of the game like the legacies are.