"Roar" was, is and will be bigger. Only Taylor would have top it. The fact that it's the fastest digital single ever
Although ugh, I can't keep seeing her decreasing

I know, the song is a monster and everything but it would be awesome if Katy is able to keep selling 300k
And about Britney, I think you're overestimating her. Yeah, she is a big digital force. But thing is that Miley and Katy are on massive overall points. Miley has the insane streams and Katy is almost dominating every Hot 100 component

Plus, I don't see Britney being hell high on Streaming, she's lucky if she debuts at #3 on Streaming Songs chart, but I see her debuting like at 6-12 region