Although I feel the opinion expressed by most that opening another SIG 
would disperse energy, and thus attention, is most surely correct; I 
also feel that an ARM sig could make sense if focused correctly.

While the embedded sig may focus on bridging and solving the 
shortcomings of embedded platforms lacking a complete operating system, 
the ARM sig may focus specifically on high-powered boards able to run 
full-blown operating systems (Raspi, Panda, Odroid, and so on).
These are another world to the usual embedded systems, and spawn a 
different kind of problems: library and package availability over 
specific distros, specific capabilities support (like hard-float) and 
thus compile chains setup, and others.

Rosserial, openembedded, uROSnode... these are not of interest to those 
running debian or ubuntu distros on their ARM, as well as the bare-metal 
implementations which would defeat the purpose of all these high powered 
ARM boards.

I think an ARM sig could be very useful if both it and the embedded sig 
are focused properly.

Regards
Claudio