Obsolete
There is always change and improvement, and there is always someone who bought a product before a particular cutoff date and misses the new price or the new operating system or the new whatever. This is life in the technology lane. If you always wait for the next price cut or to buy the new improved model, you'll never buy any technology product because there is always something better and less expensive on the horizon. The good news is that if you buy products from companies that support them well, like Apple tries to do, you will receive years of useful and satisfying service from them even as newer models are introduced.
It's easy to be annoyed when a newly released piece of software doesn't work on your not-yet-old device. I'm looking at you, iPad 1 owners.
Unfortunately, there's normally a reason for it.
As Marco points out, when the original iPad shipped in early 2010, it ran iOS 3.2 and supported very few background tasks. For this reason, the compromise of including just 256MB of system memory seemed fair at the time. However as iOS matured, the need for background tasks such as iCloud and third-party music apps has demanded more memory. Now the lack of RAM seems like an oversight; a poor design choice. "Why can't my iPad run iOS 6? Apple is trying to make me upgrade to a new iPad just to give them more money!"
It's important for gadget buyers to remember that the first generation of a new product is likely to have more compromises than later generations. With any version 1.0, creators put the fruit of their labours out into the world and watch everyone discover, explore and criticise the hard work that went into them. Whilst any company should always be learning from their existing products, I imagine the releases which teach creators the most are the 1.0s. These releases give the most insight into how the product is used, what works well and what needs to be improved.
A good test for this theory will be to see which changes are made when the iPad mini is updated for the first time. Will the screen be the big compromise of the first generation? Will it be the CPU? Something else?
It's important to note that buying products based on what they can do today is important. Don't assume your device will be updated for years to come. Don't buy a device because you expect an important feature to be coming in a future update: wait until the feature you need is available or find something else. This will lead you to be more content with the products you have. You'll worry less about devices you own being obsolete and focus more on enjoying what you own.
The technology world is always changing. Technology is like a piece of music; you enjoy it for the journey itself, not reaching the end.