Its not a fork of Puppet, Satellite ships with its own copy of Puppet (3.6 iirc) which it integrates to provide the configuration management side of the product but its stock un-modified puppet.

In fact the puppet side of Satellite is built around Foreman (http://theforeman.org/) which is an open source project that isn;t Red Hat controlled so even if Red Hat wanted to move 100% to Ansible it would be very hard work for little gain. It would also be a really bad commercial idea Puppet is by far the market leader and most of their customers buy satellite precisely because it integrates with their existing puppet manifiests.

So I expect Puppet to stay as Red Hat's goto configuration management tool, and ansible to be used more for its ad-hoc remote execution capabilities where puppet is nowhere near as good. RH already uses ansible in the installer for Open Shift for example because it can set up multiple boxes without needing an agent pre-installed.