I should clarify that the 70,000 aren't long-term support people, but rather, temporary Filipino workers who will build the base housing prior to the move of the military and their families. So, the 70,000 will be off-island by the time the families start moving in.
There is unlikely to be significant long-term support jobs associated with the presence of these 8,000 Marines. The numbers I've seen estimate the creation of 200 total new jobs on-base. There will probably be a small increase in off-base business (mostly bars, night clubs, etc), but I doubt it'll result in a huge influx of off-islanders looking for jobs... hell, there's plenty of unemployed people on-island right now looking for work.
However, while the influx of military wont directly necessitate an increase in flights, the raw materials needed for the buildup may (though most stuff will come through our Port).
Additionally, the GAA (Guam Airport Authority) is currently executing a long-planned expansion of the runway in an effort to attract more tourists/business. I've heard chat of hopefully attracting an EWR-GUM direct flight. The military buildup is cited as one reason why this runway expansion is needed, but the airport construction would have still happened with or without this buildup.