In obtaining court orders rather than warrants, police in both Riley and Graham seem to have followed the law and the generally understood constitutional guidance of Smith and similar decisions, and their practice was consistent with decisions in other cases (in other circuits) as recently as a few months ago. In short: the authorities were following the Constitution. The Fourth Circuit panel majority thought otherwise, apparently in part because of the large amount of data requested and received based on one of the court orders.
Due to the split between circuits, the Supreme Court is likely at some point to resolve the issue. If they rule that the search in Graham was a Fourth Amendment search requiring a warrant it would be a tightening of the present standard. If they rule the other way, things revert to the status quo, which has been the standard since 1979, more than 35 years ago. Either way, there is no possibility that it will be "part of the slippery slope where we find ways around the Constitution".
While it is somewhat off topic, the NSA metadata collection was done under the same legal interpretations, more or less (certainly a bit strained to say the least), under a law enacted in part with intent to authorize continuation of a program that nearly everyone agreed was not legal. NSA obtained quarterly orders from a competent court directing carriers to deliver metadata. Since then a different court has made a determination that the Patriot Act did not, in fact, authorize that and the program has expired and one hopes is winding down as provided in the recently passed Freedom Act. Whether this collection was a Fourth Amendment search is, I think, undecided as yet and probably moot.