Adobe has recently released the Beta of its' next major update to the Flash Player - on Abobe Labs - and this time with HD Video support. (Amongst other general improvements) From a few other reports I've come across, the final version is expected in a couple of months, and of course other Flash-based products like Adobe Air will also benefit from the same technology.
It'll be interesting to see how fast the takeup is with sites like youtube or dailymotion. And compression? FLV (Flash Video) compression is awesome. (Stroke of genius by Macromedia - hiring Sorenson to do it) But I think full-on HD Video might be pushing the limits of it.