Device time to the public could be either right away or take some time. It all depends on how fast the hardware makers jump onto the technology. Look at how slow USB 2 has been to catch on.
I would say, if there is a device that catches your eye at the expo, or soon after, then grab it. I would also suggest speaking with as many developers as you can and find out who has devices in the works. If they are showing devices, then try and get them to give you a solid time frame for release.
I remember seeing the P5 glove at last years MWNY, which was originally supposed to come out last year. As far as I know, it has yet to hit the market.
Take everything there (except from Apple or large companies) with at least a few grains of salt.