First, it confirms our first choice during XO reboot, working with XAPI. As you know, XenServer is based on it: we are on the right way to integrate XO in a complete XenServer environment.
Then, we start to think about a way to deliver XO out of the box with XenServer. Despite we're not here right now, we think it can be very powerful to build virtual infrastructure quickly and without installing any software to manage it.
Stay in touch, we'll push a news on XO by this week end.