In this paper we theoretically study a novel approach for soliton-induced supercontinuum generation based on the application of metallic dielectric-coated hollow waveguides. The low loss of such waveguides permits the use of smaller diameters with enhanced dispersion control and enables the generation of two-octave-broad spectra with unprecedentedly high spectral peak power densities up to five orders of magnitude larger than in standard PCFs with high coherence. The predicted high coherence of the supercontinuum is related to the coherent seed components formed by the abruptly rising plasma density. We also predict that high-power supercontinua in the vacuum ultraviolet can be generated in such waveguides.