I can't speak about the quality or relevance of work that's been done in the
sub-ip area; I simply haven't followed it closely enough.
However it's clear to me that the Internet has an increasing need for
commonality in services that are (depending on how you think about them)
either between IP and layer 2, or "alongside" IP. For example we really
need a uniform way for hosts to authenticate themselves to the network,
one which works beyond the local link and doesn't resort to tunneling.
We also seem to need a uniform way for packets to authenticate themselves
to other networks that they traverse.
So maybe there are problems with with the current sub-ip area, or maybe
there aren't - I really cannot say. But even if we choose to shut down
that area then we shouldn't use this as a reason to not do work in that
space. At least, whether to continue the current sub-ip area and whether
IETF should do work in that area should be separate discussions.
(and frankly I can't imagine another organization better positioned to
do work in the areas I mention above).
Keith