ISS will be well supported. The Japanese have their ATV (Automated Transfer Vehicle), the European Space Agency has their ATV (ATV-2 is docked to the ISS right now in fact), and the Russians have Progress, so there's plenty of cargo hauling available.
On the passenger side, right now all crew changes will occur via Soyuz (which, since the 2 Soyuz capsules are also the "lifeboats", it's the best way to go anyway because they have to be rotated every 6 months and is why all crew changes have been done via Soyuz for the last couple of years), but
SpaceX launched their Dragon capsule in December and plan to launch it again several more times this year with the second of them being the first "live" flight with cargo. After that they will also begin "passenger" certification, so we'll probably see it used to lift crews as well within the next few years. They are slated for 12 cargo resupply missions to ISS between now and 2015, well in advance of what NASA had been planning to do with Constellation. Also, Orbital Sciences is working on their own cargo vehicle as well, so they may be ready within 5 years as well.
Thing is, even before Constellation (the Space Shuttle replacement) was canceled last year by Pres. Obama, there was going to be a 5-7 year gap where the US would not be directly supporting the ISS with launches until Constellation came online, so the 2 ATV's, Progress, and Soyuz were the planned mode of support during that period anyway and NASA had planned it that way back after Columbia when retirement of the STS became an all too real issue.