I don't know yet, but I'm glad that the entertainment industry doesn't know neither.
So LG just designed a player (LG BH-100) that plays Blu-Ray and HD-DVD.
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I hope that the other companies will react in the same way to the "Disc-Format-Dispute". In some years I might possibly buy my movies on HD-DVD and Blu-Ray and at least 10 more types of discs, cubes or whatever else will come.
But as long as the movies are good, I don't care what type of player I need to watch them.