Expectationmanagement may be as important as the particular plan, or lack thereof.
Arc is unusual in that there was some activity very early on followed by a very long period of little publicly visible activity (prompting much speculation), then a flurry of activity since its release in January. So, the expectations of how Arc might unfold probably vary widely.
Is pg gathering feedback to go back to the lab for a few more years in silence, or will there be a consistent effort to work toward a '1.0' release, and if so, approximately when will that be, or is the plan something else entirely?
And maybe I'm the only one who has these questions :)
Given that Anarki exists and appears to be updated reasonably frequently, it seems likely that, unless pg does something, sheer genetic drift will cause Anarki and ArcN to diverge enough to become separate and incompatible dialects. If someone makes a killer app in Arc, and uses Anarki-specific extensions, it may very well be that merging ArcN into Anarki may be too difficult and possibly even counterproductive (e.g. if too many names in an Arc3 conflict with names on Arc2-based Anarki).
If it goes on for longer, both may even evolve into entirely different languages (like Scheme and CL). Might make a good study of memetics and the origin of programming languages ^^.