The B737 used to be Boeing's "cash cow" with most of the development costs covered long ago. Now they are selling again but at a steep discount, and airlines are pushing back delivery dates for the B777-X. The B787 may be the major earner for the company over the next few years as operators downgrade to smaller types.
It looks like Boeing will be competing with Airbus more on price then anything else for the medium term, and by the time a replacement type is available, Airbus will likely have something new as well.