I read this article and the comments following it and I figured it was an interesting topic. Obvisously some of the older gamers here enjoy co-op, which is a different set of the features normally seen in games. By keeping co-op in mind are developers going to get a piece of that older gamer crowd?
Some of the suggested changes to allow disabled gamers to play I have noticed in Valve's famed co-op series Left 4 Dead. Most notably the captions of the special infected sounds, which help even if you do not have hearing problems.
I agree completely with the comments that the issue is not a lack of ability in older gamers (at least not the majority), but a lack of a variety of gametypes and just unique implementation of known genres. Also I suggest looking at genres that have not seen much if any action recently. Like the American Western games or the slower stealth games. Make them current, but don't lose the core values of these and you may just engage older gamers.
I have no qualms about developers adding features to increase accessibility for gamers with disabilities, but I do think a proper esitmate of expected earnings will need to arrive before they get their gears churning.
And lastly, I think it's funny how the report suggests developers need products to appeal to these demographics within 5 years or the loss could harm the industry. Five years? That does not leave much time for the developers and publisher to fool around.