That doesn't look possible. Updates to stable are very rare, and in this case we would need to push a rather uncomfortably large set of changes. If there is a simple and confined patch to fix this, that would be fine, but I don't see it.
Hi Norbert,thank you for letting me know. That's unfortunate, although the difference in the last digit of the XeTeX version seems minor to me.
I guess, in this case feel free to view it as a bug report against the xetex version in testing... (I did not try to install the version from unstable/experimental so far, but if it is brand new, the bug is likely to be fixed there.)
Best, Leon