"Birthday" is the next OBVIOUS smash hit on the album and needs to be the follow-up to "Dark Horse". It also has more international appeal because of it's disco dance sound and Katy needs a global hit right now (Unconditionally and Dark Horse are not doing much outside of America).
The next obvious hit is obviously the pop-urban-rhythmic crossover hit, "This is how we do". The only reason I want that to be the next one is because it will easily extend the shelf life of PRISM by taking over the same demographic that DH is filling right now.
Legendary Lovers should be the next one after TIHWD though, and only because it will easily top the pop charts. It's too "pop" though, and any crossover audience appeal that DH brought into PRISM might be lost if LL becomes the next single.
I see Birthday taking off ONLY if the prior single truly smashes. Birthday doesn't add anything to PRISM's ambitions too, other than being a moderate hit, unless they remix this as a throwback pop hit with Bruno Mars. "Double Rainbow" SHOULD be released around Grammy time in 2016.
I thought you had good taste, miss.
