In fact, research by Microsoft has discovered that plug-in free sites are becoming more popular than plug-in sites. Microsoft "examined the use of plug-ins across the top 97,000 sites world-wide, a corpus which includes local sites outside the US in significant depth. Many of the 62% of these sites that currently use Adobe Flash already fall back to HTML5 video in the absence of plug-in support. When serving ads in the absence of plug-ins, most sites already perform the equivalent of this fallback, showing that this approach is practical and scalable. There’s a steep drop-off in plug-in usage after Flash, with one control used on 2% of sites and a small collection of controls used on between 0.5% and 0.75% of sites."
Microsoft envisages most of these sites moving to HTML 5 in the near future.