After the retirement of the space shuttle, whenever that happens, supplying ISS with needed consumables and new equipment will have to be done another way. Russia and Europe have cargo ships to take more of that task, and Japan is ready to launch its first unmanned cargo ship.
The Russian Soyuz, at present, will be the only vehicle capable of delivering people to ISS and bringing them home, although Europe is considering developing its own manned spaceflight capability. Various U. S. private companies are also trying to develop a private manned spacecraft capable of orbital flight.
Japan is working under an interesting restriction. If it can't launch this month, the launch will be delayed until February so as not to interfere with the nation's fishing season. The fishing industry is an important piece of the Japanese economy. Japan's launch facility is on the coast, and fisherman don't want spent rocket stages crashing into the Pacific scaring away their livelihood.