Yes, the 4090 is a good value if it performs like Nvidia claims and if the prices are in the ballpark of what they listed.
I'm not sure what availability will be like... will the high-end market be indifferent after such a long drought... at this point, some people are probably trying to figure out whether it's worth purchasing a 30-series or wait for the new products.
The GeForce RTX 30-series is mature (and upgraded with the Ti products) and the drivers should be relatively stable, likewise regarding the hardware power and cooling implementations, mux output, etc.
I can see the 4090 and its relatives being popular for content creators (i.e., graphic rendering, etc.), given the significant performance improvements that could pay for themselves very quickly.