It sounds like you can only scan data into the Amibos for 1 game at a time

I'm more sure of this now.

Amiibos are selling terrific from a lot of reports coming in from the internet.

While they're OK to use in Smash, they really need a more Amiibo-centric game to be able to keep Amiibos selling IMO. Nintendo's gotta jump all over this and keep the momentum going, this could be a nice gold mine for them.

Having them only do little bonus things in a few titles just isn't enough I think. Amiibo could be big if Nintendo makes it a central part of their business.

They will release this in august.
But will not be a huge game. I think will be digital only and for free. Just for selling amiibos.

And more like disney infinity than skylanders.

Nintendo doesn't believe in the "freemium" model (which is effectively what that would be). 

Plus it should be a disc game IMO so it has a retail presence. 

I could see the core game being cheap though, like maybe $39.99 for the game, or $49.99 with an amiibo bundled. 

A simplistic platform puzzle game yes it's for kids. Note I'm not saying puzzle games are for kids I'm saying captain toad is. As far as amiibo go, I don't think Nintendo has much of a plan at all. Their implementation thus far amounts to costume dlc and a cpu sidekick. Not to mention the limited write capacity.