After Jan 2016, It looks like UAL will have to reduce the number of 70 seat aircraft to 102 to increase the number of 76 seat aircraft to the maximum of 153 allowed by the scope clause. Even if UAL adds a 100 seat narrow body, which will increase to number of 76 seat aircraft allowed by scope, the optimal number of 70 seat aircraft will remain 102.
So, who is losing 70 seat airplanes? This would really only effect CRJ700s and E170s.
The link below is the simplest description of the United scope clause. It's 3 years old, but I don't think the clause has changed since then.
Look for Bigger, More Comfortable Airplanes at United Express | The Cranky Flier
This link isn't current, but has a fairly recent breakdown of the UAX fleet.
https://sites.google.com/site/united...fleet-tracking