There's another important reason that the Jones case is not as good as it sounds. The Court only partially decides whether the government can engage in GPS tracking without a warrant.

In order to determine whether the government violates the 4th Amendment, the Court must answer two questions. (1) Did the government activity (i.e., attaching GPS tracker to a car) qualify as a "search" or "seizure"? (2) If so, was the search or seizure reasonable?

In the Jones case, the Court ONLY answered the first question, because the government based its entire case on the argument that attaching a GPS tracker is not a search. The Court found that attaching a GPS tracker to a car does indeed qualify as a search, but did not determine under what circumstances it might be reasonable to conduct such a search without a warrant. So, in a future case, the court might determine that it is reasonable to search (i.e., attach a GPS tracker) without a warrant because, for example, the car might be moved before the warrant could be approved. In fact, it is already the case that cars can be searched without warrants in many cases where houses, personal belongings, etc. cannot be.

(Note that the Court uses the phrase "reasonable expectation of privacy" extensively, but this actually has nothing to do with the reasonableness of the search. It only determines whether a search occurred.)