Chris is more relevant than Rihanna these days. Loyal alone >>>
Nobody is saying Rihanna is over (at least I'm not) but she's not making the right choices at the moment. And if she keeps picking blah songs to record, the biggest producers and songwriters are gonna stop offering her their best. And that's when she'll be over because it's not like she has the talent to create a good song herself.
And I do think Ariana is creeping up as Rih's "replacement". They seem to share a similar market.