No-one expects indefinite support. The problem is that the Galaxy S was released only 16 months ago, and is still available in some countries. And the Galaxy Tab is only 13 months old, and is also still being sold.
The comparable situation from the competitors would be if the iPhone 4 couldn't be upgraded to iOS 5.0.
In reality, Apple is still supporting the iPhone 3GS (released a whopping 30 months ago) and the third-gen iPod Touch (released 27 months ago, discontinued 15 months ago). Apple has never stopped supporting a mobile product they're still selling, or even one they've sold sometime in the past year.