I do not think so. Voyager did not have great ratings and Enterprise didn't either but it is not that difficult to redo Enterprise since it is only the visual effects rerendering and reediting from the original film telecine HD tapes.
They will eventually do all of them including Voyager (IMO of course)
Enterprise was always in HD so no extra effort or money needed there, the visual effects were rendered at HD from the start. The show was broadcast in HD in the markets that were ready and has been shown in HD on the HDNet channel the last few years (and looking damn good).