Get ready for layoffs, if the deal closes you will be hit. In a major way. Trust me, I've been thruough with my company. Most likely overlaps will be in HR, Finance, IT and Marketing - you will see some cuts there - depending on how they go about it projects will likely be affected.
I am thinking that you may expect a 3 to 5% cut overall, I have no insider info, this is just based on my experience.
Good luck to all who work for Rockwell Collins, I spent 3 years there from 2011 to 2014.