It's unlikely that seating will be any less crowded, so what does Boeing foresee as significant changes in the design of its cabin interiors? It's all about lighting and projection.
Airlines want customers to like their aircraft and want a way to make the experience on their brand to be a different and memorable, to help distinguish it from its competitor. That's hard to do that with hardware -- cabinetry, overhead bins and such (although sliding doors between cabins are quite cool!) But it can be achieved with aircraft accent lighting and the development of projections of light and images on the ceilings, walls and such. Boeing engineers are actively working on these designs.
Projections could be of virtually any scene the airline desires -- a beautiful cloudy sky, a nightscape filled with stars and planets, a natural scene, perhaps from the destination you're flying to. There's a lot an airline could do once the system is installed, as changing their theme is quick and relatively inexpensive.
There was no target date announced for when these innovations will appear on planes.