bhyve would have to support what is called "PCI-E passthrough", and support such functionality via IOMMUs to allow device-initiated DMAs to work (which GPUs, >=10gbit NICs, storage controllers, etc, all require).
KVM, Xen, and ESXI all support this, so if bhyve doesn't support it yet, it most likely will in the future.
I don't have an answer to your question but note that bhyve is still very new, it is still very experimental, and the feature list is still pretty short. That said, work is ongoing and progressing pretty quickly.
1) http://www.bsdnow.tv/episodes/2015_12_16-im_talking_about_th...
2) https://twitter.com/michaeldexter/status/676290499389485057
3) http://pastebin.com/4BQ5uVsT