My personal take after viewing dozens of titles from both parties is that they will more than likely co-exist similar to DVD-A and SACD. Although I personally have seen better titles and quality on HD-DVD. For example here are the absolutely KEY TITLES:

THE SEARCHERS
GRAND PRIX (70mm film in HD)
BATMAN BEGINS (one of the best for sound)
CASABLANCA
Mutiny on the Bounty