From my cursory look, pg has fixed many if not most of the core issues that anarki resolved. (ie cut fn not handling -1, providing a static directory for files to be published, added some basic math functions - sin cos etc..).
I would suggest starting a new branch with arc3 and if the libraries from anarki are still relevant then people will incrementally add them. This way were not integrating a bunch of code just because it's there - even though it's no longer useful.
+ just because you make them work with core arc3 files doesn't mean there will not be conflicts - as example the int function in the anarki math.arc library conflicts with news.arc only (as pg added an int function).
Some of the things anarki adds that are not in arc3 are tremendously useful.
For example, help strings and the 'help macro to access them, and similarly, the ability to call up any function or macro's source with 'src.
I do think the idea of integrating anarki code incrementally is probably the right way to do it. To this end, I've forked anarki's "official" branch (http://github.com/rntz/arc), and I've been applying CatDancer's "minimum-distance-from-arc" patching philosophy (http://catdancer.github.com/sharing-hacks.html). We'll see how many things from anarki I end up converting this way.