Your 50% in 3 years sound about right. But it is guesswork. If there will be much nicer batteries available, less than it. If batteries will be just a bit better (10-20%), it will still be doing alright, as it drives so well - my guess.
Thanks for the input. There is of course possibility of "Tesla effect" where the price don't drop as much as there is not much units (Taycan's and competitors) in used car market. Also direction of going electric might play in same way.
For me there is mainly two points to consider;
1. The progress of EV's
2. The progress of batteries
In interview on Top Gear (twice) Chris Harris have told that Porsche just touched the technical limits of EV's and could have made much better product.
This makes me wonder what that could be?
Probably the EV as a platform won't be that much better in "Taycan 2.0", tech will be better as always, but motors etc. similar, so no big difference.
The batteries might be the one which goes forward most and maybe they are lighter and hold more capacity, which might make things difficult for the 1st gen vehicles.
The lease residual value in the US is 51% after 3 years so losing half if its value sounds about right.
I honestly think it can lose even more if by that time it there are other sport EVs with more range in the market (Etron-GT, Macan EV, Mustang GT, etc) or if the Taycan's battery end up with degradation issues.