On the flip side of this, how much "development" can you realistically expect from a pair of shoes?
Sure you can make them lighter and more breathable than before (look at shoes now compared to yesteryear and you'll see clear advancements) but there's only so much you can do.
There's no point trying to re-invent the wheel each year, if it ain't broke don't fix it. If something does come along that would add value by all means do it, but it's not like there's anything wrong with the existing product as it is.
Also, as it't the same product with just the colours changed, you can get some right bargains by going for an "old" pair of shoes that's on sale!