I haven't done any testing of it, but supporting STUN on the same port as SIP is a requirement for an edge proxy supporting outbound. So I don't think it should be obsoleted or removed.
peter,
my understanding is that stun server as specified in ice rfc 5245 authenticates its clients, but there does not seem to be any possibility for the server to know the realm of the connecting client, which mean that a single realm must be configured in the stun server.
if that is true, it is not possible that a single stun server serves more than one domain at the same port. so does what you write in above mean that in multi-domain sip proxy setup, kamailio must be configured to listen at different ports for different domains (which in my opinion is not realistic).
-- juha