In the following scenario, does the person have a reasonable expectation of privacy?Assuming the police may bring a dog to "sniff" a vehicle...

Given the facts you have provided, and assuming this was a
routine traffic stop, and there is no independant probable cause to search the vehicle,
no, you may not detain the vehicle and occupants beyond the time required for the
traffic stop itself.

However,should there be independant
probable cause to search the vehicle- the smell of marijuana coming from the vehicle for
example- then you make briefly detain  the vehicle and occupants while you search (you
are now conducting a "Terry stop"), and you may bring the dog to scene. The question of
how long you make detain them while searching/bringing the dog has been the subject of a
number of appellent cases over the years, and there is no hard and fast
tule.