Quite reliable rumours are that the stage from Pau will end at Lac Payolle, a little lake at the early slopes of the western side of the Col d'Aspin, after the descent of the Tourmalet.
An optimistic stage design would be something like this:
This means an approach from the west, an approach from the east with (Port de Balès), Peyresourde, (Col d'Azet) and Aspin/Hourquette d'Ancizan is possible too.
The stage to Andorra will start from Vielha and likely end in one of the usual suspects: Pal or Arcalis, without Gallina. But I hope we get Gallina - Comella as final climbs with a finish in Andorra la Vella.
Morzine/Avoriaz and Les Gets as stage 19 and 20 are by no means a certainty, as said by Thomas Vergouwen at his site. From a geographical point of view, it would be more logical to have them earlier (but from a geographical point of view going to Bern from southern France and then descending back south isn't logical either).
Less reliable rumours go that the stage from Bern will either be Bern - Châtel, followed by a stage to Avoriaz and the TT, or Bern - Avoriaz (with Pas de Morgins and Col de Corbier before the mtf), followed by the TT.