As far as I'm aware, Thinking Of You isn't certified 2x Platinum, so Katy's streak is ultimately broken just by her first era.
Rihanna and Taylor also have PLENTY singles which didn't reach 2x Platinum.
Applause is already over that, but DWUW is definitely eligible for a double platinum certification if Judas was.
So, if MTN didn't break the streak, she would have had 14 consecutive double platinum singles. GUY would have failed it either way, so it's almost the same ****.