p2p

1) Smaller, long range A/C with good CASM allow point-to-hub traffic, as you say, but therefore reduce the demand for slots at the 2nd hub that those passengers were previously flying through. So for example Portland to Narita reduces demand for Portland - San Francisco - Narita. San Fransico transfer traffic is reduced. A general increase in point to single hub traffic, bypassing the second hub, will reduce transfer traffic at hubs, and therefore open up slots.
2) Hub-hub-hub can be reduced to hub-hub, opening up slots. For example, a Denver to Narita flight will reduce demand for Denver-San Fran-Narita, reducing transfer traffic through San Fran. Or Pittsburgh to London reduces the demand for Pittsburgh - JFK - London. JFK transfer traffic is eased.
3) Secondary hub - to - secondary hub or point - to - secondary hub will reduce slot demand on the previous hub-to-hub routes. Eg: A flight from Portland to Osaka or Kansai will take the pressure off of San Francisco or Seattle and Narita. (Decentralization). Similarily, Toronto to Birmingham takes the pressure off of Toronto-LHR-Birmingham. Transfer traffic at LHR is eased.
http://www.airliners.net/discussions/general_aviation/read.main/3197713/#63