I don't think they'll do a Mario Tennis series. I think the Super Mario series will be continued and used for Mario spin-off titles. I think by launch, we'll likely get the second wave of Mario series featuring some characters that aren't in Smash but are in Mario spin-offs i.e. Toadette, Waluigi, Birdo etc.
TBF, isn't amiibo Festival a free title, but with a retail presence with a bundle of 2 amiibo figures and a pack of cards? I'm not getting it anyway, doesn't look interesting enough for me.
It's a grey area. They need to find a balance that can please everyone, but when people complain about the most minor uses, they're going to get complaints no matter what.