In an update from the earlier story about plans for tonight's Hell in a Cell match, Dave Meltzer reported today that it was just a decision they made to move the match up to SmackDown.
As noted earlier, Reigns and Mysterio will actually wrestle tonight inside the Hell in a Cell and this is not an angle to set up the match for Sunday night.
In fact, Meltzer states that Reigns will not be wrestling on the pay-per-view on Sunday night and Rey and Dominik Mysterio will not be facing The Usos either. The tag match was something that people were speculating on earlier today but it is not happening.
The match and finish planned for tonight is what was originally planned for the pay-per-view. As noted earlier, the folks at the USA Network are not happy about the match being pulled from Peacock and then given to FOX.