Last I heard the property owner Ron Logan was released from police custody. It's hard to tell if suspect was wearing a hat/hoodie in the two still shots. If guy in the picture is not wearing a hat and that's his hair, then that would eliminate Ron Logan as he has shorter gray/white hair. With the exception of the hair Mr. Logan looks like the suspect in the picture.
I read that both victims had scarfs around their necks during the funerals which leads me to think they either had their throats cut or strangled. Probably strangled as Abby survived the attack and died of hypothermia a few hours before the search party located the bodies. As BTK confirmed it can be difficult to kill someone from strangulation and I doubt he intended to leave Abby alive.
I've been over at Webslueths discussing this case and not really much is going on, great site though. Police are not releasing much and probably for good reason.
The more time goes on the more I think the killer must have been a local.