Excuse me? Or were you only referring to Sony there?
No one dare change it lest alienate gamers and developers who find the alternative, like the Wiimte, to just plan SUCK for a lot of established, successful, and enjoyable titles.
The evolution of the gamepad has typically been an upward one that was compatible with previous incarnations. Moving from the NES (Dpad+A/B) to the SNES (Dpad+A/B/X/Y+2 bumpers) didn't prevent SNES games from playing NES style game mechanics in their full glory. Neither did the N64>SNES or GCN>N64.
Nintendo fans may not care and casuals may have no clue, but the end of the day is that games like a Madden suck on the Wii relative to their console counterparts because the Wiimote doesn't map well to the game at all. So while the changes to the 360 and PS3 controllers were friendly to the evolution of a proven software design the Wii took a bold new approach, netted a new audiance, but alienated another.
And it would be shocking if MS and Sony both said, "Lets make Wiimotes and no longer support a 6M selling franchise like Madden." We call that surrendering a market.
On a tangent, I think people are mistaken if they believe everyone has to make a "Wii" to be successful. Last gen it was everyone had to do a PS2 (cutting edge optical, expensive processors, etc) and before that the PS1, and so forth. One thing that is clear is that we now are seeing some stratification in the consumer market based on hardware lines--something we haven't seen so clearly before where harcore enthusiest and self-titled "gamers" gravitated to one end and the casual market to another.
One thing is for sure is that if MS or Sony vacate the "enthusiest" segment (which is about half of the current market--a segment that also buys a lot of games) is that it will leave this market to one player. From this perspective I really doubt MS or Sony will blink too long because neither would want to conceed to living room trojan.