It will increase some but nowhere near as much as last time. Artists are already creating assets at a much higher level than actually ends up in games for various reasons. Additionally it's the number of assets that really makes the difference now we are at the point of visual quality we are at now. Procedural and dynamic assets will help mitigate raising costs in other areas. Dynamic cloth physics will mean that animators won't have to hand animate cloth, Dynamic lighting means you don't have to bake it in etc.
A lot of the increases in costs this gen weren't to do with graphics anyway, more better voice actors, mocap, licenced music, more advertising, online etc have all been on the rise this gen. Then there is the fact as the average age of the people in the industry increasses so do wages, plus there is a lot more legal and cross licencing these days. Most of these things won't go up all that much next generation (exept maybe voice actors as big actors start to be put into bigger roles).
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