According to a FAQ released for the upcoming "Better Together" Minecraft update, Microsoft wants to bring it to PlayStation 4 and wants to work with Sony, it also confirms that Microsoft is indeed in negotiations with Sony: https://minecraft.net/en-us/article/better-together-faq
Q: Will the new version be available on PlayStation 4 and Nintendo Switch?
A: While we are thrilled to be able to confirm the new version of Minecraft is coming to Nintendo Switch, we are still in discussions with Sony about PlayStation and have nothing to confirm. We would love to work with Sony to bring players on PlayStation 4 into this ecosystem as well.