That is true.
Does the Pope consider the issue of celibacy to not be open to discussion as well?
The Pope doesn't want to talk about it, but celibacy for priests is not dogma, nor is it even a teaching.
Sinky, it is at least a discipline.
One could also argue that insofar as it is a VERY long-standing tradition, affirmed in writing around 300 AD, that it has the force of permanent law.
Seems that many of the posters on this thread have forgotten about Tradition, which is fully ONE-HALF of the 'Scripture and Tradition' foundation of Church teaching and law.