actually, it's nothing at all like the flu.
There are two proteins found on the outer shell of influenza. These are H (hemagglutinin) and N (neuraminidase). There are 16 known types of H and 9 known types of N, which if you do the math leads to 144 different combinations of the proteins on the outer shell. What the scientists do each year is look at what combinations are appearing in the spring/early summer, and based on that come up with the best flu vaccine for the coming year. As there are 144 combinations, there are years where what they design ends up being a somewhat ineffective flu vaccine, as the H and N combination that becomes predominate may not be ones that were addressed by the flu vaccine. The scientists are not projecting mutations of influenza; just what H-N combination will be most prevalent.
There aren't a lot of mutations with the influenza virus. There are small mutations, called antigenic drift. These cause small changes in the surface proteins H and N. Occasionally these antigenic drifts cause small problems where antibodies created by a case of the flu, or from a flu vaccine, may not recognize a strain in the same season that is the result of the antigenic drift.