650b
 

Do you think we'll reach a point where the market is big enough to have more and better tire offerings? The thing that stopped me from looking at the 650b Straggler was the relative dearth of tires available. A fair amount of MTB type stuff, but little in the way of street tires...and no snow tires.

You must not have done much looking. There are quite a few great "street tire" offerings in 650B (Grand Bois, Compass, Soma, Pacenti, etc), and Nokian/Suomi makes a studded tire, the A10. I think Schwalbe might as well.

http://www.innovatires.com/tire_serch.php?xPA=IA-2572. (27.5"=650b)

650b by Panaracer, Surly and Sunlite.

http://search.bikeman.com/search/ind...+tires&x=0&y=0

I think you will find more and more tires coming up in the near future in 650B to add to the already decent marketplace. Schwalbe makes a ton as does Panaracer (probably many on the above lists and most of the ones from Rivendell are made by them) and there are other makers around.
650B Tires

The more the platform gets used for the road the more stuff will come out for it. Just like road tubeless and discs more and more will come out when it gets more popular. However generally most of the technology goes towards racing so sometimes tourists, commuters and general cyclists are left out of some of the major brands here and there for different reasons.