That would require it to cross the Cascades. While anything north of 80 is pure fiction at this point, Oregon may be the last state I'd expect to build another mile of new freeway, especially through national forest lands.
I think politically, there's a challenge at the moment, although I have to wonder if the transition to EVs will nullify that within a decade-or-so. It's one thing to be a Climate Doomer and say "We are drawing the line on freeways," it's another thing to be a Climate Doomer when 80% of your friends and neighbors are driving by battery powered by wind, solar and water. Maybe that's a pipe dream, but it's a hopeful one…
As for crossing the Cascades, the lowest pass is also the pass that makes the most sense for this project – Government Camp, at 4000'. It's rarely completely closed – and is often used by truck traffic when I-84 is closed through the Columbia River Gorge due to ice and snow (its elevation tends to protect it from the severe weather that hits at sea level, giving it more steady snow vs. the ice/snow mix in the Gorge).
More importantly, as Portland and Bend have grown, so has traffic on the 26 corridor, closing in on 11,000 ADT west of Government Camp and more than 6,200 ADT south of the Mt. Hood Meadows turnoff. Those are on par with other rural western interstates. And Bend remains the largest US city connected to the rest of the world exclusively by 2-lane roads. It's outright dangerous, and at some point, people are going to get tired of being scared to drive that road.