Max has a big brain theory which sounds like a likely scenario. Because Yuffie has a different personality from the original game than she does in this trailer that she will undergo some transformation in this DLC that will make her become the character she is in the original game (which will be in the next part of the remake) - Probably being that jobber she's with in the trailer dies or something.
Remake is very heavy on character development and I don't think this DLC is going to stray from that idea. It's likely going to be very important in the long run.