Since Renoise has samples, not really OSCs, it is difficult to implement a real OSC sync. I am not saying this is not possible, but it certainly would require a new concept for some kind of a special oscillator / single cycle / wavetable mode instead a resampler/player. So this would require a lot of effort and time, conceptual, programmatical and also design-wise, so I doubt that this will be a topic at all (since there are so many other more obvious points)
Much more easily to implement would be a ringmod cross-sample mode, or a sidechain for the ringmod device. Still even these simple solutions could not compete with a real osc-based/synthesizer-based conception, but would give interesting new sound possibilities at least.