John Nemesh :
If there is more than a single game (very, VERY likely) that support multiple trackers, I will buy a few! Hell, I am already in it for $2800 (PC + Vive), what's another $300?
I think that's what Valve/HTC are banking on with the accessory ecosystem.
I think it will eventually be pretty common for Vive owners to have two or three trackers and an array of accessories for them, such as these foot and belt clips and the various guns we've seen.
Someone really into shooters might consider picking up a Rifle, one or two pistols, and maybe a shotgun peripheral to cycle through. I could even see a generic mele-type weapon that could be used to mimic swords, crowbars, or chainsaws.
So much possibility. Especially for VR arcades.