You're right, Adriana is the only irreplaceable. Some people are comparing Sara with her but Sara has to grow a lot to get on her feet. The charm and beauty of adriana are unique and no one will ever be able to be equal or compare to her, especially Sara who always seems obsessed with wanting attention. I understand VS have choose Sara as angel but the power of brunette is with Taylor Hill , beautiful and good in catwalk.
I agree with a lot of what you said.
I think because Lima was/is so huge and super for Victoria's Secret and as a household name, it will take the combination of both Sara and Taylor to get the public comfortable with the absence of Lima, at least for a while. See Taylor was smart and started to use the hashtag #Saylor because she knows how good that will be for her PR, if she was part of a new trend.
I think it's unfair to compare Sara and Taylor who are both gorgeous and powerful brunettes but not as powerful single vs together as Adriana is by herself. Taylor is more High Fashion and Sara is more swimsuit/commercial in comparison it seems, at least so far (I hope Sara can do some high end stuff too, I'd love to see her do some Dolce & Gabanna or Chanel ). So for Victoria's Secret they become Saylor and we get a combination of two aspects of the fashion world.
Hopefully, Saylor will stick around because I love the concept.