Nope not for me as I am not a cat type person and have nothing against them, but as a gimmick how is this going to last and then what happens to the cats? Firstly you coffee has to be spot on and not half arsed which it sounds like so maybe 3-6 months and this will be gone. I have had two cats in the last 10 years who were both strays and just stayed so I am not anti cats, but more neutral and have no appeal for this type of gimmick.
I think if they can keep the smoothies looking good they will be fine. Smoothies are all overpriced in this part of town anyway because it is tourist central. The tourism aspect of it is also why I think they will survive at least for a few years. Tourists come and visit the place once and then their room is filled the next week with new people that don't know the cat cafe is overpriced swill that they don't know how to make very well.
Seeing as how the cats are older than the cafe is, this may be a troupe of cats that work in cafes all over the place. Hell, they might not even be the property of the cafe itself but are just rented. If that sounds crazy there are crazy rental schemes here in Vietnam, so it wouldn't surprise me at all.