[XeTeX] embedding PDF, 1.4 vs. 1.5

[maxwell]

Late last year, I ran into a problem in which I could embed a PDF v1.4, 
but not v1.5 (I have not tried this with newer versions of PDFs, which 
are now up to 1.7).  The problem and its work-around are described here:
    http://tug.org/mailman/htdig/xetex/2012-October/023677.html
also
    http://tug.org/pipermail/xetex/2012-December/023869.html
and in the preceding and following messages in those threads.

The problem bit us again today.  Fortunately, we now know the 
work-around.  But my question is whether this is likely to get fixed in 
some future version of xetex?  (We're using the TeXLive 2013 version = 
3.1415926-2.5-0.9999.3-2013060708.)

    Mike Maxwell