You are very welcome! Glad I could provide a modicum of useful info.
As SectorOne pointed out, because all teams' ICEs will suffer in the thin air, the PU hierarchy will more or less stay the same.
However, because of the problems that arise due to the thinner air (e.g., the issue of additional heat dissipation), teams that can run efficient cooling solutions may suffer less than other teams.
The top teams are also capable of doing some seriously in-depth tuning (including of course, mapping) to adjust various ICE parameters in order to mitigate altitude-related, negative effects on the PU.
That turbo really helps mitigate power loss. It just has to work its tail off. And the turbo working harder means that the MGU-H is pushed harder as well.
In sum, cooling is going to be the name of the game here. Engine cooling shouldn't be a huge problem. But teams are going to open the cars up as much as possible to help cool the PUs, the gearbox, etc.
Oh, and this race is tough on the brakes, too.
Hope that helps.