You can already work with ProRes footage in Vegas with no problem - no export though and I doubt you'll ever see it. Avid DNxHD is how we get back to FCP albeit slow as molasses out of Vegas.
Last time I tested this the Sony YUV codec which we do have in Vegas is compatible with FCP. It's certainly compatible with Ppro and AE. We get it in both 10bit and 8bit as well. Add MacDrive to your system and bouncing files to OSX/FCP systems should be fairly easy. Also the Cineform codecs should be / are compatible. Only problem is both parties have to pay for them.
If all else fails uncompressed works with anything, monster file sizes for sure but portable 2TB disks are off the shelf items these days.