Many of these receivers can apportion any un-used channels for distributing audio to other areas of the home. In addition for dedicated media room applications the additional channels can be configured for use with moderately priced in-ceiling speakers for height channels. Yamaha for one offers up to 11.2 with it's RXZ11 offering which can be configured as a 5.1 or 7.1 receiver plus a zone 2 and zone 3 speaker level distribution receiver. For clients seeking moderately priced whole house a/v distribution these new receivers offer a lot of bang for the buck.

I also know that on one of the higher end 7.1 channel marantz recievers if you were only using 5.1 you could use the extra two channels to bi-wire the front speakers.

The problem is three fold. One, there's no such thing as too many channels in theory. Two, most people can't get beyond 5.1 very easily. Three, there is no really good standard.

I propose this - 12.4 for recording and playback. It is a good system for several reasons. One, it is enough to handle any of the existing systems. Two, it is a base 2 number of channels, so it is actually the next logical jump from 7.1 8-channel systems.

The system is comprised of the following -

3 existing front channels, 2 existing side channels, 2 existing rear channels, 1 subwoofer channel

And adds

2 extreme width channels at 60 degrees off center front as suggested by many
2 height channels as suggested by many
1 overhead channel as suggested by many
1 extra subwoofer channel for stereo bass
1 extra subwoofer channel for rear bass/bass correction
1 visceral effects channel for bass shaker type devices

Each receiver would typically come as a basic 7.1 design and extra amps could add extra channel capability or you could scale to the recording to the number of channels you have, regardless of your speaker configuration.

OTOH, one of the saddest things is the lack of middle or high quality 5.1 receivers on the market for the people that only need and can use this.

I think all that you need is one extra channel in the front, a high or low center channel. That would give 3-dimensions for positioning objects on the screen if each of the four channels were discrete. Then an extra sub with room-equalization would help, but you're not going to get stereo separation form them. Below 80Hz you can't really localize where the sound is coming from and it should blend into all of the other speakers. An extra sub just compensates for poor room design or sub positioning.

9.2 is not a great improvement over 7.1 as 7.1 was not a huge improvement over 5.1. I will most likely take a miss on it unless I hear a side by side demo that just floors me.

The reason quadraphonic did not catch on is basic: It did not work! For example, some consumer media release formats did not allow rear left-to-right panning while many professional recording consoles did not allow front to back panning. Broadcast FM was capable of 3 channels had the industry chosen, but not 4.
Quad was promoted for music which sees little, if any, benefit from rear speakers other than for ambiance.

Why 9.2 and not 10.2 as postulated by Tomlinson Holman of TMH? The routing part of the decoding in the new Dolby/DTS systems was also not mentioned as it should have been.

Finally, it would appear that the LFE - or .1 - channel is still misunderstood! Two subwoofers do not .2 make. The LFE channel is a dedicated channel and a 9.2 or 10.2 (or even 22.2 from the NHK) system has two dedicated LFE channels, possibly with different frequency ranges but certainly with different signals.

There is enough confusion about multichannel sound without adding to it.

Why 9.2 and not 10.2 as postulated by Tomlinson Holman of TMH? The routing part of the decoding in the new Dolby/DTS systems was also not mentioned as it should have been.

Finally, it would appear that the LFE - or .1 - channel is still misunderstood! Two subwoofers do not .2 make. The LFE channel is a dedicated channel and a 9.2 or 10.2 (or even 22.2 from the NHK) system has two dedicated LFE channels, possibly with different frequency ranges but certainly with different signals.

There is enough confusion about multichannel sound without adding to it.

9.2 seems like overkill to me. I have a 7.1 system but very little media or TV have anything in that format let alone 9.2. I think 5.1 is fine for most consumers. If you like electronics you can read about Wireless Home Theater System on my website