Well, looks like these keyboards will be available soon! I'm seeing them on the websites for Sweetwater and Sam Ash in the U.S. for pre-orders. Both sites have the PSR-E473 for about $370, and the PSR-EW425 for about $490 USD.
The prices for these keyboards are definitely creeping up, but you really do get a lot for your money. When I got my PSR-E433, it was about $250. Compared to that keyboard, these new models add...
About 90 more sounds
About 100 more styles
Double the polyphony -- from 32 to 64 notes max
Dozens of DSP effects
A second channel of DSP
Super Art. Lite
Motion Sequencing
Style revoicing
Style, voice, and transpose freeze
Tunable scales
Audio input
Digital audio recording capability
Sampling capability
Reverb/Chorusing for the style
Enhanced DJ effects
Throughout all of these additions over the past decade from the E433 to the E473/EW425, we really haven't lost that much. As far as I can tell, all that has been taken away is about 70 prerecorded songs, a stereo-wide feature, and when going from the E463/EW410 to the new keyboards, the ability to play a sampled sound on the keyboard. Of course, the lower-quality feel of the keyboard after the E433 has been discussed before. We'll just have to wait until we can actually play an E473/EW425 to see if Yamaha has improved the key feel.