We always expect that the newer offerings will be an improvement over the older models, but that isn't always the case, is it?
Sometimes a company puts out a product that is very good and this product becomes very popular. Then the company wants to increase the profit margin and puts out a follow-up product using less costly components/construction techniques and the performance is compromised. Or else the costs in materials or construction become so high that a product that was once feasible becomes cost prohibitive. That's why certain models become classics and are highly sought after long after they've been discontinued.
Of course it works the other way, too. For example, the receivers we're discussing here probably better JVC's older $170-$250 offerings that don't use the new Hybrid Feedback design.
So it's really hard to tell. These new JVC receivers sure have some really great features. Hopefully the sound quality will be just as good or even better than the F10 and ES1sl. I guess we won't know until they come out.
It's interesting to me that many people on the forum think the older ES1sl is more tube-like and, arguably, more musical than the F10. Because of this discussion, I returned my just purchased F10 and bought an ES1sl instead. All the information suggested that the ES1sl was more in line with what I preferred in terms of sonic character. I've been very happy with it.
If I were your position, Buddy, I would take advantage of my dealer's return policy (without abusing it, of course!), and return the F10. After the reviews come in, you can decide whether the newer amp or the F10 is more to your liking and make your decision from there.
It would suck to think you made the "wrong choice" because you made your purchase a month or two too early to compare.
Best,
KT