This came up in December last year when the Portland Business Journal first
covered the news, but is re-surfacing now in the
Oregonian (their first story on the topic). I'm sure some people missed it the first time around.
Called the "Terminal Balancing Concourse E Extension Project," the project would move Alaska Airlines from concourses A, B and C onto concourse E, while moving United Airlines from concourse E to concourse C. The project would also extend concourse E by 210 feet and improve ground loading facilities nearby.
I am going to have to try and enjoy the Country Cat as much as possible in the next year and will really miss the D/E security checkpoint!