Nobody will change bike on the descent. That would be utterly nuts.
If there's a bike change, it will happen at the summit, going from a climbing bike to an aero bike (probably TT setup) for the descent.
The first 6km of the descent will be at 100+ km/h, so almost certainly in an aero tuck, pedalling a massive gear where possible (even a 55x10 is 144rpm at 100 km/h). The 10 (depending how you count 'em) switchbacks in the final 5km will be taken fast; as technical as it may look, I suspect the riders should be going through those corners at high speed, so a TT bike might still be the way to go.
The question, IMO, is if the climb is steep enough to offer a benefit to using a road bike. To me, it doesn't look like the slopes are steep enough to force a good TTer out of the skis for much more than accelerating out of the occasional corner.
6-7,5 % is "flat" enough so that the aero gains from a TT bike could be quite significant. On the other hand at 7 % weight also plays a role, so that extra ~1,5 kg isn't negligible. Then there's a position on the bike when going uphill and, as you said, a TT specialist who feels comfortable on the TT bike will more likely choose this one, while non-TT guys, climbers (like Carapaz Chavez etc) would probably prefer to the uphill section on a road bike.
Then comes the descent. I haven't heard about 10t sprockets in road cycling honestly

They will have a standard 11t with probably at least 58/60t chainring at the front (which interestingly still gives a smaller ratio than your example and that's btw why introducing 10t sprockets in mtb was kinda revolutionary). The first half of the descent (also less steep one) is practically almost a straight road so that's where they're gonna make use of those 60t chainrings. I don't agree that the speeds on the switchbacks in the second part will be that high. They will have to decelarate quite strongly, then immediatly take up the speed and repeat that 10 times - TT bike doesn't have a huge advantage in this part cause they won't be able to use aero tuck position + it handles considerably worse on the switchbikes comparing to standard road bike.
All in all. For the first part of the course, the uphill, TT bike could be slightly more effecient, but that applies mainly to TT specialists. The first part of the descent (~5,5 km) is where you can take the biggest advantage of a TT bike (and I think that is the decisive argument for a TT bike), then, on the switchbacks, it's imo a little bit slower.
So I predict there will be two scenarios: 1) road bike then swap for TT bike for non-TT specialist 2) TT bike from the start to the finish for guys feeling more comfortable on TT machines.