The ISN is dead. They may be having one last meeting or they may not, but either way it's being wound up. As always in such circumstances, most of the nominal members will drift off into inactivity or single issue or union activism. Of the ones who were still active at the end, some have moved to RS21, some to Left Unity, some to the Greens. Ironically, the small number signing up for the Greens tend to come from the wing which was more "left wing" and sceptical in its approach to Left Unity.
It seems like a pretty demoralised milieu, having been through a major split, a failed courtship process, another smaller split that may have been the stupidest in the history of the left and now the death of their group.