There was a thread in which Adriaan Moors replied to @virtualeyes that xml literal syntax
is, and has been for a while now, "effectively" deprecated.
There is a GSOC project to start a macrotized interpolator for XML as first step to spinning off and divesting XML support. The interpolator is expected to support pluggable libraries.
An XML interpolator was envisioned in the interpolation SIP, together with quasiquoting, so this has been in the works.