After just recently finishing an essay on a similar topic I thought this could be an interesting topic for discussion. At the least it will provide us with a talking point for a few days.
Anyway on to the topic. Personally I think that games design in the future will not only challenge players in new and divergent ways, but also challenge the developers to create new games that haven't been done before. Or to create games that are played in a new way.
I think that as technology improves and games become able to do more, perhaps the design of games will have to change to incorporate not only sight and sound, but also the other three senses. Who knows perhaps in the far, far future we will have more senses with which to play games with.
Perhaps virtual reality is the way forwards with games. The technology is always improving, and while it isn't a widely accessiable technology yet, it does seem to be something to look at in the future. They could even replicate all the five senses within the game environment. Even now they are trying to replicate smell within a virtual world. The Matrix films for example really did show us the potential that a virtual reality system can have.
But the future of design in games doesn't just have to come from new technologies. It could also come from some bright spark of imagination. Games don't just have to be designed around what a player see, but rather what they hear. We have already seen this in to a point in Moddb.com, Blind Monk's Society. Just imagine what a full game could acheive if the player really had to listen to what was going on instead of relying on the usual markers to get from one objective to the other. Only time will really tell where design in games will go, but there really are a million and one possibilities. Many being perhaps only small in scale, others being vast in scale and hopefully changing things for the better.
There is no right or wrong answer to this topic, but it would be nice to see what people think on the future of games design and where it might head.