# cat /etc/release
Oracle Solaris 11 11/11 X86
Copyright (c) 1983, 2011, Oracle and/or its affiliates. All rights reserved.
Assembled 18 October 2011
# pkg info entire | grep Summary | sed 's/.*[\(]\(.*\)[\)].*/\1/'
Oracle Solaris 11 11/11 SRU 8.5
Or perhaps, yet:
# pkg info entire | grep Version | sed 's/.*[\(]\(.*\)[\)].*/\1/'
Oracle Solaris 11.3.1.5.2