Comment by shakna
Whilst I can't be certain, I've been hearing that part of Google's want to move away from XSLT is two-fold - and relates to the idea of the security problem.
Partly, there's increasing attacks against XML.
And also, libxml2 has said "no" to security embargoes altogether. [0]
They might well consider there to be 0-days waiting in XSLT.