Unless Britney retires and doesn't come back that's the only way I see her becoming Irrelevant.
Otherwise she immune to it. And I wouldn't even bring up her talent into this, because if it was a factor for her which it isn't and never was she would have been irrelevant a long long time ago. Plus she has a extremely loyal fan bases to ***** her out to the public so she is fine. Beyonce is also immune so she's safe as well. Katy & Rihanna i'm not sure about them.