aroraborealis

It should be - I haven't read the relevant rfid radio specs in a long time, and I am not a radio hacker (we keep hams and EEs around for that), but I expect it should be fairly trivial to attach multiple chips to the same antenna. The two questions that come to mind are what are the relevant wavelengths (which would control minimum antenna size and possibly spacing of the rfid chip attachments from each other) and if the signal could be attenuated by having parallel circuit paths to the different radios, but I think that last isn't actually a concern (and actually comes from a slightly broken understanding of the relevant physics). But it's early yet, and I haven't had my coffee, and we should find a radio geek and ask them.

And then try it.
Muahahaha...