No one came up with anything new from a PCM processing perspective (improvements to MRC have been suggested for a long time). Of course, Meridian are the experts and "apodizing" subsequently came out of the blue.
My guess is that the apodizing filters, increased output channel support, increased processing power (e.g. to decode *and* upsample DD/DTS bitstreams), MRCv2, SpeakerLink outputs, 8-channel SpeakerLink input, a new ADC card and new DAC cards are all examples of items which 861 owners will benefit from first. How important these might be to you, I can't say.
Meridian is always going to come up with something new that surprises all of us, but I do think that, digitally at least, we *are* on the verge of perfection. I think it's likely to be small incremental improvements and clever features which happen in the future.
Good summary VK. Apodizing filters and improved MRC would most interest me, and it appears that the G has the horsepower for at least the former. Maybe unlikely, but a more advanced MRC might require more MIPS and a new card for the 861. I remember Bob Stuart saying the main difference the 861 sounds better than the G is that you can keep video out of it.