IBM and Red Hat will still compete on providing services after the sale, but technical support will be shared by the two companies.
Does Red Hat currently make more on technical support or services? If the latter, then they might be in trouble competing with IBM which has a huge Linux group now.
It's easy to hide from IBM's Global Services Division. They don't really want to mess with anybody who isn't going to bill at least $250,000 a year in services. Stay out of those places, and they will be your friend. Many, many companies make a nice living from the crumbs that IBM sweeps their way.