Over on the GeForce Now Reddit a user called SammyFae has discovered that Phantasy Star Online 2 is showing hints of GeForce Now support. When you try and run the game it is displaying the error message that the game is not fully supported as yet.
Usually when this message is displayed this means that the game is likely to be on its way to the service. Last week Two Point Hospital was released on GeForce Now which is also a Sega game. Hopefully this is a sign that more Sega games will be added to the service shortly.