As long as the Xoom is the only Google Experience 10" tablet on the market, it certainly will. Once the Xoom's successor comes out, I think that'll be the end of official OTA update support from Google.
I would imagine the Xoom would get future Jelly Bean updates (like 4.2) no matter what, but I would be shocked if it got any updates past Jelly Bean unless there still is no Xoom successor by that time.
Due to the fact it is a Google Experie device just about any version that hits AOSP will be able to be run on it until such time as they completly drop support of Tegra 2 or do something to the OS that the physical device just can't support.
The Kernel is flashable so it will never be a problem provided there is a developer out there willing to work on it.
And any AOSP version will be supportable with the right Kernel...
There is ONE limitation I can think of where the Xoom will be unable to run the latest and that is if the OS expands in size as far as the /System partition is concerned. I know Team EOS JB Stingray is very close to running out of space there and if the next flavor of android adds a lot to /System it could be difficult to squeeze it into the unit.
But I'm sure there is a workaround for that too.
You may not get direct updates from Google (truth is they only really handle the Wingray anyway) but you will easily see support from other sources here until the Devs dry up and move on or the Unit just is too old to run the latest.