The manipulation of radiative properties of light emitters coupled with surface plasmons is important for engineering new nanoscale optoelectronic devices, including lasers, detectors and single photon emitters(1-8). However, so far the radiative rates of excited states in semiconductors and molecular systems have been enhanced only moderately, typically by a factor of 10-50, producing emission mostly from thermalized excitons(2,6,9-11). Here, we show the generation of dominant hot-exciton emission, that is, luminescence from non-thermalized excitons that are enhanced by the highly concentrated electromagnetic fields supported by the resonant whispering-gallery plasmonic nanocavities of CdS-SiO2-Ag core-shell nanowire devices. By tuning the plasmonic cavity size to match the whispering-gallery resonances, an almost complete transition from thermalized exciton to hot-exciton emission can be achieved, which reflects exceptionally high radiative rate enhancement of >10(3) and sub-picosecond lifetimes. Core-shell plasmonic nanowires are an ideal test bed for studying and controlling strong plasmon-exciton interaction at the nanoscale and opens new avenues for applications in ultrafast nanophotonic devices.