Okay, so I cashed some favors in and actually got some face time with the Fantom-G. Spent about 30 minutes shooting questions and sucking up a LOT of information—to the point where my brain hurt and was asked "Audacity, are you writing for a magazine now or something?" The only reason I'll be able to spew forth so much is that I took tons of notes and am currently sitting in a Marriot hotel room (thanks, Leslie!) a couple hours later. So I hopefully won't screw this up and give you guys wrong information. Suffice to say, nothing here is 100% confirmed and everything is subject to change.
Overall impressions and other stuff I learned about the Fantom-G:
1. Roland is incredibly excited and proud of the G. There was definitely a buzz in their booth.
2. Here's a little trick I learned long ago: If a manufacturer doesn't have a hands-on area for their new products, chances are its OS isn't finished. Therefore, as only demonstrators were able to touch the thing (well, and me after all sorts of payola, bribes, and sexual favors), that points to the OS being premature. So we might be able to sneak a couple of minor requests in, but nothing hardware-based (polyphony or I/O). A few of my (and your) questions couldn't be answered, because the OS simply isn't 100% done. Especially the sequencer.
3. The sound is decidedly Roland. I noticed a few familiar patches, but was told that "the ROM isn't finished. We have more samples to add." However, the sonic quality is without a doubt a major step up from the X. I'm not sure if they've stopped using compressed data or what, but the overall sound is very, very good. More open, clean, and punchy, but again, still certainly a Fantom. When I asked about the engine, some guy in a suit said "It was redesigned from the ground up, utilizing new chips." Regardless, if you don't like the sound of Roland ROMplers, you probably won't like the G. Personally, I think they fit pop, hip hop, and rock music better than the XS or M3. I was told that the sound set consists of "classic Fantom patches, selected sounds from all the SRX boards, and a bunch of all-new stuff". As I understand it, the majority is not recycled. Asking for a definitive ratio seemed pointless.
4. The screen looks AMAZING. It's not just a bigger Fantom screen—the resolution is iPhone or laptop-level. Windows are semi-transparent, there are icons galore, there's a ton of visual feedback when playing keys or twisting knobs, and unlike the Motif XS, screen redraws are instant. It's way better than even the V-Synth GT's screen.
5. The UI is definitely Fantom-esque. They still have the MENU button (blech), still have the SHIFT button (yay!), but everything seems to have been streamlined. Navigating appears to be faster and easier—No separate WRITE and SAVE/LOAD buttons, no separate SAMPLE LIST and SAMPLE EDIT buttons... The screen is big enough to avoid too much scrolling, and the mouse seemed to work without a hitch (pointer looks identical to the one in OSX). Unfortunately, I didn't have a chance to see how the mouse works with editing audio/MIDI.
6. 22 effects processors. That's right—TWENTY TWO effects processors. There is no "source" parameter in the effects routing page because it's not necessary. All parts get their own MFX processor. More info in number 9 below...
7. No more PATCH and PERFORMANCE mode. There's now SINGLE mode, which is kinda like the old PATCH mode, LIVE mode, which is a 10-part multitimbral layer/split mode, and STUDIO, which is an 18-part multitimbral sequencing mode. Wait—10 and 18 parts? The ARX expansions are considered extra parts; they don't eat into the sixteen internal parts (and they have their own polyphony!). What's a bit weird is that in LIVE mode, the pads/rhythm are on part 8 (because 9 and 10 are reserved for the ARX expansions) and in STUDIO mode, the pads/rhythm are on part 10, like in almost all other Roland ROMplers. That might get a bit confusing, especially when jumping from LIVE to STUDIO mode.