Most people have done that with their posts, and it's what I'm doing now:
At the point of sale, you should be deciding whether what you are buying is worth the money you are exchanging for it, even with the possibility that newer products can come out tomorrow or in ten years.
If you feel that newer iPads, on their current release schedule, damage the value of your previous purchase so badly, the obligation is on you to not buy those products (since their value is so precarious), not on Apple to stop selling. Just because you feel bad doesn't mean Apple is doing anything wrong.
Appeals to 'premium price' don't hold any water because 'premium price' is subjective. Apple never said "If you pay this price, which we have presented as a premium price, then we will delay product releases as you see fit". It's a silly inference to make.
Appeals to 'true lifecycle' don't get you anywhere either. How do you know what the 'true' lifecycle is (as opposed to a 'false' lifecycle)? How does the new release change what you bought?
Why is £649 a price which entitles you to your grievance and $500 isn't? At which price does it flip from 'normal price' to 'premium price'?