I don't even understand why this is even an issue. The M9 is over 10 years old now, although granted its derivatives are not. Are there other 10 year old cameras whose sensors are still available?
Because people love their M9 and can't get it repaired...even at crazy Leica prices for repair. As far as other 10 year old cameras... they haven't failed yet and if they do, people will move on or buy another for $200.