Even though I love BA much more then WANEGBT, i don t want it to be the second single, well at least, they shouldnt send it to radio until the album release, it s just so Lady Gaga-ish (3 singles annonced before BTW) and it didn t work !!!!!
It will kill WANEGBT exposure since people will focalize their attention on BA and she could end up with a declining lead single & a "new" second single during RED's date of release

About Adele, I think she didn t reach the star power of Taylor yet despite her colossal sales, she s just the one who bring unanimity but few people really stan for her, remember during the AMAs, she was during her heydays but she lost to Taylor in the Artist Of The Year award ( a fan voted award).
Rihanna is coming faster ...#9 however it makes it more interesting
