No, not really, as it ignores all the specifics of the situation which matter. The current leading implementation of Perl 6 is Rakudo, which is implemented in NQP (itself a subset of Perl 6 that's meant to be easier to implement and optimize), which is comparable in some ways to rpython. At the point you already have an intermediate language, a lot of the benefits of using PyPy and being able to write your language in a higher level language aren't as much of a gain. Additionally, using PyPy would lock the implementation into whatever current limitations PyPy has (threads?). MoarVM is not the back-end, it's one back-end, and one meant to optimize specifically for NQP's needs.

I imagine at some point a PyPy targeted Perl 6 will appear. It may or may not be based on the Rakudo implementation as a target for NQP (jnthn was able to get initial JVM support for NQP completed in a summer), or another implementation that targets PyPy through rperl directly. It would be really interesting to see what Perl 6's automatic opportunistic auto-threading of list operations and PyPy's STM work could do together.