I wonder if might see UI fashion go full circle and come back to this style at some point. The flat style of the past 5 years came in reaction to the over-rendered skeuomorphic look that had been growing out of control. But I feel like when I look back at what Windows and Mac OS looked like in the 90s, it almost feels fresh again. It doesn't attempt to look like a photo, it just uses very a simplified, graphical style of light and shadow to hint at affordances and visual hierarchy.