Thinner and lighter is fine for the Air, as long as they bring back a full set of ports on the Pro.
A Pro machine should include the ports needed for Pro work, without having to carry a bag full of dongles. It should include HDMI, USB-A, and Ethernet.
A pro machine should have the most flexible ports possible so you can attach whatever device yo need to at the time, which is USB-C; rather than limiting you to legacy formats such as USB-A and ethernet, or even HDMI, all of which can be connected via dongle.
USB-C gives pros, and everyone else, the ports they need for work; especially if you're already carrying the cables attaching an adpater to the end is minor vs. being stuck with legacy ports.