Andy Murray is fairly certain that women could play best of five sets if they really wanted to do but it shouldn't be forced by the WTA.
Tennis is an ever-evolving sport where things get discussed all the time. Changes are being done nonstop as the sport tries to keep up with the times. Some of those changes are quite positive like the electronic line system which aims to level the playing field for all players minimizing mistakes.
Some changes are socially driven such as the Wimbledon underwear changes which aim to make it more comfortable for women to play at the event instead of enforcing a rather banal rule which made many of them uncomfortable.
There have also been discussions about women potentially playing the best of five sets at Grand Slams like men which would possibly have beneficial effects on the sport. Murray, a self-described feminist is certain that it could be done though he doesn't want to see anything enforced against the will of players.
If it was something that the women were completely against doing and they were being asked and the tournament were really pushing them to play best of five sets then maybe that’s a different discussion there but my understanding is that that’s not what it is.
If the women were asked to play five-set matches I’m sure they would be more than capable and more than willing to do that. But I don’t think it’s their decision … so that’s the end of the argument, for me.
Time will tell whether we see something like that in the future though most players would likely oppose it. Naomi Osaka famously brushed off the topic suggesting that men play best of seven sets then. I don't personally think they would like that very much.