The latest on the county webpage on the project says, "November 2023 – Project design is moving toward 65% stage." Since design isn't finished, and the project manager indicated in the October 24, 2023 Berkeleyside article (when design was indicated at 35%, but not updated since September) that environmental clearances are expected by the end of 2024, and anticipated Spring 2025 as construction start, and these things rarely get started before anticipated, I'd go with Spring 2025 as the earliest construction will begin.
The MUP should be there awhile (and, unlike most MUP's, it has very few pedestrians/runners, and is wide enough to easily avoid them if they are there). As the signs warn cyclists, you COULD see an EBRPD maintenance vehicle between El Toyonal and Inspiration Point, but that has to be extremely rare, and really, it just means don't ride the wrong side of the road in that stretch, but it is a bad idea to ride the wrong side of the road even between Camino Pablo and El Toyonal, because you might crash into another bike.
The road from Insp Pt to El Toyonal is also used by residents and horse people who live/board horses/etc. on El Toyenal, everything up to and including horse trailers. I have personally seen a horse trailer, a couple big working pick-up trucks and a random car or two on that stretch of road since the washout. I would characterize the likelihood of seeing a motor vehicle there as "rare" but more than "extremely rare." It is not likely on any given ride, but if you ride there regularly, the odds are you will see a car/pick-up on that stretch of road. As long as you are paying attention, it isn't a problem.
Everything from El Toyonal to San Pablo Dam Road is a hard no-go for anything but bikes, pedestrians and horses.
One more thing - be extra careful on Wildcat during leaf- falling season, especially when it has just rained. In normal times, the wind generated by cars driving on it sweeps most of the leaves off the road. Without that wind effect, more leaves stay on the road. That means more leaves than usual on the road after a rain. More leaves means more wet leaves, which in turn means a slicker road surface. Slick road surface plus downhill speeds plus twisty turns - well, you can do the math.
As Michael Conrad's character used to say on "Hill Street Blues," "Let's be careful out there."