I think Dave has it right; the ART7 is actually improved over the ANV50, even though the latter cartridge cost or costs more (depending upon whether either or both are still available). The introduction of the ANV50 preceded that of the ART7. Maybe the hypothetical "ART10" will incorporate the technology of the current high-priced ART1000, where the coil is located just above the stylus tip. I'd love to hear that one, but not own one for $5,000. We're going to Japan next month, and I will look around for the local price of the ART1000. I doubt it will be cheap enough to justify my taking the plunge.
For what it's worth, I have read the comparisons of the ART7 vs the ART9, where reviewers AND Audio Technica say that the ART7 is not so good for jazz and rock compared to the ART9. In my experience on my Beveridge system, that's a bunch of hooey. The ART7 is very dynamic. That is one of its greatest strengths. The dynamic aspect of its sound is related to what I wrote above about emphasizing the leading edges of transients. At the beginning (first few hours), this quality was bordering on fatiguing, but at this point the cartridge has gotten a lot smoother, bringing out the instrumental details better than it did at first.
Is it really true that 2juki products are "gray market"? What does that mean, in this context? The phrase arose back in the 80s, when certain foreign cars could not be imported into the US, because they did not meet our then new requirements for emissions and etc. Some privateers imported such cars and converted them within the US to meet spec or as near to it as they could get away with. The parent companies would not honor the warranty on such cars, because they couldn't vouch for the longevity of components in cars that were modified. Nothing like that is going on here.