Mal

Well, textures yes. But things like effects, lighting, animations and such can all still be very much improved and certainly optimized. There's plenty of room left to grow.

Now we just need to hire artists who know how to make something more interesting than dirt and explosions. =)

I think the bottleneck will only come if the industry wants it. Graphics aren't the only reason that development costs are going up and with the improving tools of the trade, I think the cost of graphics is going to go down in the next few years.