Bravo! for early planning and infrastructure investments.
I probably won't be driving in 35 years, but if I am I want my damn flying car where we'll get that versatile 3rd dimension for travel lanes.
I actually drove in the area near 35 years ago as well. The distance seemed much farther without the new development and driving on 35 was terrible because they were just starting to widen the highway.
Today there are more viable routes and lanes to get between the 2 cities, and with the help of some apps you can get around the bottlenecks when they pop up so it's actually an easier commute these days.
Still, the idea of more improvements and construction on 35 would drive me to rail, so I would rather there be other options in place sooner than later; or maybe better yet move out of the area.
As an add to the discussion, I was trying to find other areas across the country that had a similar situation to Austin-San Antonio (in terms of larger populations and proximity [~74 miles]). The closest seem to be: Charlotte-Greensboro [83 miles], Louisville-Cincinnati [83 miles), and maybe Baltimore-Philadelphia [90 miles]. I'm not that familiar with how any of these areas interact, but it is interesting (to me at least) to think in terms of distance what might be a similar situation. North Carolina seems to be the closest comparison.