Didn't Boeing say there are going to be two options? One enginemaker would be kicked out at the start, and the other two would both come up with new engines. Boeing is also looking for major gains in efficiency, so the chosen companies will be making either an all-new engine or a varient with major changes.
The comittment to two engine suppliers shouldn't mean that one will be kicked out right from the start. Maybe we will end up with a similar scenario as the A380 did, one company and one joint venture.
As the development costs are not getting cheaper at all, and as there are already examples on joining forces (CFM56, V2500, GP7200) I kind of expect to see at least one new addition to this list powering the 7E7.