Adding wifi to a LAN Bridge for Xen

[ray <ray@aarden.us>]

I have a LAN connection on a laptop with jessie designed for a Xen installation.  The /etc/network/interfaces looks like:

auto lo
iface lo inet loopback
allow-hotplug usb0
iface usb0 inet manual
auto xenbr0
iface xenbr0 inet dhcp
bridge_ports usb0 

I would like to add wifi to this such that transitioning from a wired location to a wifi hotspot, there will not be an interruption; or if one of the service are lost, the machine can automatically use the other.  

I have seen a dual Ethernet card implementation model for redundant cards for the host and any of the guests.  
It seems like the way to do this with wifi would be to include another bridge associated with the wlan0.  Would it be functional to repeat the usb0 and xenbr0 stanza and replace usb0 with wlan0 and xenbr0 with xenwbr0?