Developing good motion controls is one of the pain in the ass aspects of developing for the Wii.  Unless the developer feels their is an audience that justifies the added time (and thus expense) to develop the controls they aren't going to add them.  It really is that simple.  The attach ratio for the peripheral would likely have to exceed 20% to be meaningful and honestly there isn't much chance of that.

What would be the point?

People are buing into the Wii because they want the intuitive and innovative controlls that Nintendo (and certain third party developers) are putting into high quality exclusive Wii games.

Sony and Microsoft could do it but NO ONE would buy into it ...

Brand name, wii is the new ipod. The zune hasn't put a dent in Ipod even though it's the same thing. Cheaper MP3 players that are just as good (sometimes better) than ipods don't even sell as well as ipods. Why? They aren't ipods. The wii is now becoming a style thing, they are featured in montages in Target commercials, they're used in new TV sitcoms, they are the "it" item. The 360 could come out with a vastly superior "wiimote" with perfect 1 to 1 controls and it still wouldn't sell as well as the wii.

 See your saying no one would buy into it, just like people said no one would buy into the Wii-more. And as far as third party games goes, we see how thats turning out. Third party developers would be more likely to make the motion sensing games for the other consoles over nintendo, because nintendo will always dominate their sales. 

 High quality exclusive games would only be Zelda, Mario, and Wii-(add word here).  Everything else would be ported to the other consoles and be multiplatform. If you enjoyed games of all types, why pay $200 more when you can get the same game with better graphics by picking up a $45 peripheral. On top of that you would get games like FF13, Halo, BioShock etc. You get the complete rave of the gaming world in one console.

 The difference is you don't hear about the many other MP3 players. Theres a difference between those and the PS3, since Sony still has the biggest name in gaming. Also, advertisement and hype would be a large factor. People are buying the Wii for the motion sensing. If people start saying "oh yeah, the 360/PS3 have those features too but better graphics." then word would spread. 

 The Wii is expected to balance out supply/demand next year. So by next christmas it wouldn't be that "impossible to find gadget." it would be "that gadget that WAS impossible to find." so instead of grabbing one as soon as your lucky enough to see it you would do more research first. 

No I'm saying that NO ONE HAS EVERY BOUGHT INTO AN ADD ON EVER!!!

People are willing to buy add ons for one game (Guitar Hero) but third parties NEVER make games for these addons ...

You can't compete with the Wii with and addon ... Everyone knows this (this shouldn't even be an argument). The Eye toy sold (something like) 5 Million units and third parties ignored it, why would they start producing games for an add on which will (likely) see smaller sales?

I actually expect MS to release a wiimote type controller soon, not to try and compete with Nintendo, but as a way to work out the bugs in the new controller before they release as the main controller for their next system. It will also give the developers a chance to get use to programming for the new controller so that they won't be behind when the next generation starts.

In other words, it won't effect Wii sales. But it was never ment too.

Playstation clearly isn't the biggest name in gaming anymore, seeing as how they are struggling for third. and Microsoft is only big in the US.

I'm sorry but I'll just have to agree to disagree. The wii is the original and would still run on it's momentum and name. The PS2 didn't suddenly crumble because two new machines that have even better graphics and more functionality (the xbox at least) came on the market. The wii wouldn't just grind to a halt because somebody else has motion sensing. How much has the six axis done to combat the wii? Nobody cares about it, and developers would likely ignore the knock off wiimote for above reasons (the wiimote60 would have a terrible attach rate, just like most peripherals do) and would get five or six games on it.

But like I said, I'm just going to have to agree to disagree since I doubt you're going to budge on this idea.

NO NO!!

& I don't even want it to happen

I am very happy with the Dualshock 3.../sixaxis

I think with the progression the PS Eye is making, the next generation of Playstations might come with that and start to support it in every console, maybe have it sit on top of your TV similar to the wii, but menu's and stuff could all be done with hand or what not, I'm not sure what they'll do but I can imagine something similar to that. So they'd keep the original standardized controller, but have motion support available for every game they release. I dunno just my two cents :D. And since the PS Eye comes with a decent Microphone you could also have some audio controlled games. I don't like that type personally but I think it could be interesting ^_^