She should release a follow up EP like how Cannibal was to Animal.
A fourth single would be a waste of time. They just need to concentrate on really getting the next era on point, rather than having all the flaws from the Warrior era reappear.
Nothing, continue the rest of her tour, release a fourth single if she wants too, then just get working on album #3. As a stan I'm fine with her not smashing.
Supernatural could've saved the era as the second single in late 2012, it's too late to release it as the GP won't be here for it now, and there are no remaining hit singles. C'Mon and Crazy Kids could've been good singles, but AFTER Supernatural's smash.
Thinking of You is a missed opportunity, if they don't release it. I've had non Ke$ha fans listen to it and they admit it's a fantastic song. Her flop label needs to get behind that song and to make it happen.
"Thinking of You" SHOULD smash. It probably won't, but I wish it would. If I browse my mind real quick, I think I remember "Supernatural" & "Warrior" being good tracks, too. She has a few more songs that're single-worthy, but I'm not sure what her label will do. They might just give up.
She needs to go back in the studio and re invent her sound. Ditch dr.luke, take some singing lessons and start over with a new persona. Honestly its going to be an uphill battle but at this point,drastic measures really need to be made in order to ensure some moderate success for ke$ha. I don't know though, honestly I don't see it in the cards for her. I can't see her being a serious artist and cute pop songs have no longevity and start to become redundant. Ill always be here for k$ though, if she can serve me bops like take it off and your love is my drug.
It probably won't, but I wish it would. 
If I browse my mind real quick, I think I remember "Supernatural" & "Warrior" being good tracks, too. 
She has a few more songs that're single-worthy, but I'm not sure what her label will do. 
They might just give up. 