The conventional wisdom (CW) is that some RFID tags can be read only at close range and some RFID tags only at a greater range because of the difference in the fundamental reading technology.
"Near field" (high frequency /13.56 MHz) devices rely on inductive coupling, an electromagnetic field that's essentially the same as the one used in a VCR or tape recorder. Extending this field beyond a few millimeters has always been seen as problematic. On the other hand "far field" devices (such as Gen2 UHF) use honest-togoodness RF to communicate. Restricting the interrogation field to allow for reading of a single item at close proximity has been seen as similarly problematic.
CW, therefore, dictated that HF had certain applications and UHF had other applications. However, as so often happens, CW is being shown to be more "conventional" than "wisdom."
Recent product announcements on both sides of the "field" have shown systems can be developed to read HF tags using RF (at much greater ranges) and UHF tags can be read individually at close range. What's more, it's possible to read both HF and UHF tags with a single antenna.
Taken as a whole, these advances either a) create a much more cluttered landscape when trying to develop a single technology standard for item-level tagging, or b) eliminate the need for it entirely.
From a historical perspective, we've been here before. Originally, there were two basic bar code systems for product marking: U.P.C. and the "rest of the world" Code 39 (with various coding conventions issued by different industry segments). Because computer systems were less capable than they are today—database software more limited, legacy software systems inflexible, and data content standards were so varied—it was impossible for many companies in the supply chain to use the bar codes on products because, absent overarching standards, they were essentially meaningless. Eventually, technology came up with solutions to these problems and, while there are still specialized readers for certain applications, things are now a lot more straightforward than they were 20 years ago.
The good news is that we don't face all of those problems today. ISO standards exist—and are continuing to evolve—and an unprecedented number of organizations are working cooperatively to develop consistent, uniform systems. The major struggle has been in determining how to handle RFID item (or part) level marking. Up until now, near field and far field devices didn't play well together, or even at all. That meant that a single approach had to be developed.
There were strong arguments on both sides of the debate favoring either HF or UHF. Pilot projects and tests were run that showed the "superiority" of one technology over the other (and both sides could point to results that proved that "their" technology was the winner).
With recent developments, however, the question is whether there is, in fact, a need for a single frequency for item-level marking. Insofar as pilot projects and tests have returned results that show, if nothing else, that both HF and UHF are suitable for item-level tagging.
It's too early to tell if the groups that will ultimately decide the direction of item-level tagging will choose to embrace both frequencies (and speed up item-level tagging) or postpone the decision until more data is available. The only thing that is clear at this point is that, instead of just choosing "A" or "B", there's now a third option: "C: all of the above."