Gaga's image was most definitely tarnished during the BTW era, in regards to the general public. However, I think it is foolish to say that she will completely flop with ARTPOP. She is too massive to simply die down with one flop era. I am a Britney stan, but I can recognize the success and impact that Gaga has had.
I do feel that if ARTPOP doesn't do well, she will only continue to decline. Again though, it's all a waiting game.
And Adele is NOT going to fade like Norah Jones.
