Since MS owns Minecraft and are getting a slice from it being on every other platform I don't see this point being near as strong as it could be. There is more reason for PS not to allow Minecraft cross play than Fortnite because it would be directly helping MS and the XB brand.
Here is an interesting article about PS potentially allowing cross play after the end of fiscal year 2018, so around April 2019. I've seen these rumors mentioned a few times over the last couple of days.
https://gadgets.ndtv.com/games/news/ps4-crossplay-fortnite-psn-id-name-change-ps-now-downloads-release-date-sony-1871262
It also mentions PS and their 'nearing the end of the gen' comment with an anticipated drop in sales, along with PSN name changes and PS Now offline play. This would be the perfect time for PS to announce a new PS Portable, whether or not it's tied to PS4 or PS5. Announcing a portable and the console set to launch together in 2019 would make all the sense in the world if they were also going to announce cross play going forward. PS4 won't be far off 100 million users by then, so there's no worry there, and the PS5 should have no competition for close to a year on the market. They would also make everyone who wants or requires mobile gaming, aware that they have the choice to choose a PS product as well if they wish. The potential for gamers using or moving to another brand wouldn't be near as worrisome for PS.
