If they're replacing the 4 20/236 767-400s with 772As to free up the 764s for routes elsewhere (i.e. Europe and S. America), then there's will be no new increase of flights to/from GUM and no new destination. Just more seats on the existing flights.

And right now, GUM-NRT is back to just 3 flights on most days (and only 2 on some). Switching the 764s to 772s may mean eliminating the 738 all together.