This is not yet planned. This is a proposal. Lots of us are discussing it on Fedora Discussion. Perhaps you'd like to join us?
Fedora Linux: It's your Operating System.
A community for users, developers, and anyone else interested in discussion and news of Fedora Linux
There's a discussion specifically about opt-in/opt-out on Fedora Discussion here. Per the Fedora Project Leader, "this is the first time we’re using Fedora Discussion as the main place for a Change Proposal discussion". Make your voice heard!
Who just clicks next when installing a new OS? This is not like installing a regular program. Most people I know won't even do it themselves because they are afraid to mess things up.
Imo this is a good solution. You don't send any data if you don't want to, without having to hunt down a setting. At the same time they'll probably get more meaningful results, because people tend to go with the default.
I think the least contentious thing for both sides talking would be to have a mandatory screen that asks if you'd like to do it or not. No passive opt-in or opt-out/default behavior, but instead two buttons that make you explicitly make the choice.
Like I said, it's being discussed on Fedora Discussion right now. Feel free to join.