Technical Game Designer Chadd Nervig, aka Celestalon on Twitter, has answered a tweeter's question about item squishing with the following tidbit:
.@ToppTheDwarf The item squish *will not* make soloing old raids harder. We promise, and 110% guarantee it.- Celestalon (@Celestalon) February 9, 2014
I read this, and my ears perked up. I really enjoy running around killing things indiscriminately in old raids, and I've wondered as to whether or not that would continue to be possible after the item squish. It's good to hear that Blizzard has no intention of letting older content stay as it is while our characters' ability to pump out damage is drastically reduced.
Of course, this leads to the obvious question -- what approach is Blizzard going to take for keeping older raids and dungeons' mobs and bosses abilities proportional? The obvious answer is that all of it will be squished along with our characters' gear and abilities. I suppose that will include items dropped of of old bosses too. It will be interesting to see the approach that Blizzards' designers take with the new expansion to make this change go as smoothly as possible.