State Senator Chip Shields is the first Oregon Senate incumbent to announce he won't be returning in 2017. Before this we'd only seen re-election announcements in the Senate. This will have two major impacts for Oregon politics.
The first is in electoral consequences. Open Senate seats usually result in fairly large chain reactions. Shields' announcement is no exception. House members are always top prospects for open Senate seats. The current State Representatives in Shields' senate district are House Speaker Tina Kotek and Rep. Lew Frederick. Kotek is clearly happy where she's at for the moment (seeing as since she passed up previous opportunities to run for higher office). However, Frederick was clearly aware this was coming since he announcement came 13 minutes after Shields' did. Frederick's senate run will create an additional open seat in House District 43. All of these districts are completely out of reach for Republicans.
The other aspect of this announcement is its legislative impact: Shields held spots on several coveted Senate committees. These will become available in 2017 so we're likely to see some shake-ups in committee appointments as well in 2017.