I believe that deepvocal will not support the VCV method because this method is limited to Japanese only, deepvocal is a synthesizer with a focus on Chinese, creating a Chinese VCV voice bank would be very complex. the CVVX method works for any existing language and its result is much better than VCV if well configured.
talking about XSY, probably yes! will have the XSY parameter maybe not immediately after launch, but in the long run it will! because the synthesizer predecessor to deepvocal (sharpkey) had this parameter.
about the voice’s natural air parameter, it’s already being optimized by boxstar, we can see that in the demos of deepvocal 2, the synthesis sounds more powerful, more pleasant, the air coming out of the voice is more natural and less metallic.
boxstar works alone on deepvocal, so development takes time,
about UTAU: Ameya appeared on twitter showing the new features of UTAU, however he claimed that these improvements are being too complicated, so he launched some modified resamplers and then disappeared again, it has been 8 months since we have any news or new post.