Not ever, I don't think you can really get sick of a genre unless you seriously overinvest and don't stray from it. What I am tired of is the modern fps, not fpsses(or whatever the plural form is) the modern fps. Most are interchangeable. If I played mario galaxy over and over it would get boring but if I played Galaxy, then banjo tooie, then rayman 2, then jak and daxter, then kameo or even mario sunshine I wouldn't get sick of 3d platformer collect'em all games. Because they're all different and unique. (Speaking of Kameo I should go hunt down a copy.)
So if someone makes a diferent and fun fps I'd play it. Then another if it was good.