I don't think it's a bad idea honestly, especially if they're convenient for you to start collecting now.
The switch has amiibo capabilities built-in so I definitely think AC will probably take advantage of it with the next games both with cards and probably their figures. It would be odd to have such a big, popular update in acnl and then not continue it in the next game, especially considering the Sanrio collaborations and other popular series editions that were pretty profitable for Nintendo. Hopefully they'll even do more with the cards in the future game, since some of the cards (like the special villagers) weren't really useful in acnl which seemed like a bit of a waste imo.
I would for sure. The switch can allready use amiibos and it's still popular in New leaf. Plus once the new game comes out and people start playing I bet anything the cards will go up in value and cost more.
If they work with the switch game prices will skyrocket.
I'd say try buy your favorite villagers (I used ebay for individual cards) but maybe don't invest too much just in case they don't work the same in the next installment.
I'm buying the amiibo cards whether there's an upcoming animal crossing game on the switch or not,
cause I need them for the 3ds to keep my villagers forever LOL