Most likely 2028 and Xbox by 2027. Going earlier is a risc for Xbox as the value of Xbox could be viewed a bit more negatively with these days console prices. Of the console is going to cost 500 plus dollar it better lasts for more than 6 years.
PlayStation can't wait much longer than 2028 if Xbox releases in 2027. You can't give your competitor too much of a headstart. If Xbox releases at the same time as Playstation, best case it equals this gen, which is not great for Xbox.
Please excuse my (probally) poor grammar







