Avant Force, the team (well I say Team, last I knew there was actually only my friend, Anderson Che, developing both Avant Browser and Orca Browser), have published an update on the blog, giving outlines of what's going on, with regards to Avant Browser and the much anticipated v12, previously scheduled for release both in January, then February 2010.
Sadly, v12 is still not here, we're still with the 11 series (11.7 Build 46 SR3), and yes, this series has had it's problems, the biggest of which by far, being a memory leak that causes it to crash sporadically after several days of constant use (most notably when I've went upto 72 hours or so without sleep, it's got a tendancy to either crash whilst I'm finally getting sleep, or soon after I wake up). In saying this however, the latest build is by far, the most stable of the 11 series (just as well too, or I'd not be able to use it ....).
I've spoken with Anderson several times about v12, and some of the things I'm aware of, both during the course of speaking with him, and after reading the blog (yep, work/family/development/hardware issues and hpHosts etc has me busy), is v12 is a complete re-write from the ground up, complete with a re-write (obviously) of the skinning and plugin systems (themes are rumoured to be more along the lines of those that Firefox users are familiar with, though I don't have details on that yet).
I'm just rambling now though, so I'll just point you to the blog to read up on what's happening;
Full disclosure: I've been the server/forum admin for Avant/Orca browser' forums, for a few years now, and have additionally been running the AB Archives (archive of old/current Avant/Orca releases) since 2003, and being a friend of Anderson' for years, am obviously a little biased when it comes to his projects.