Max Laier (mlaier@FreeBSD.org) has committed/merged in OpenBSD's PF system into FreeBSD -CURRENT (with all of OpenBSD 3.4's PF features). Shortly afterword the commit messages hit cvs-src@FreeBSD.org, Luigi Rizzo (luigi@FreeBSD.org) noted his opinion that importing PF would only be a step backward at this point. Do note, one of the main reasons ipfw2 is depreciated by many developers is it's lack of pfil integration, creating a glued clunk of code which is difficult to maintain.

PF port page
PF CVS foundy
Commit (mailing list) thread