This article by Zach Dundas covers the more recent decisions in the Portland metro area to create "rural reserves", locking down some areas for up to 50 years in order to preserve their status through a fickle political process. Helvetia, the farming community that Hillsboro wants to absorb, is a candidate for preservation.
Dundas writes, "The intent was to create some long-term certainty. Certainty is big for farmers, who often face decisions that can affect their businesses for decades."
Meanwhile, a case can be made for Hillsboro's desire to remake Helvetia into office parks and industrial buildings.
"Intel, the silicon-processor giant, built manufacturing and advanced research facilities here in the 1970s, and today employs more than 15,000 people in the area. Other tech, manufacturing, logistics, and research businesses piggyback on Intel's massive presence."