The "Hair" movie tossed out most of the book of the show and cut several of the songs so, no it's not a good representation of the musical. It works on its own terms though.
As for nudity, not only does it not hurt a show's chances of getting produced, it's probably more of a selling point these days than anything (look at Take Me Out, Bug, Naked Boys Singing etc...).
As for what shows we will probably never see revived, the general rule is that anything that flopped in its last Broadway incarnation will probably never attract enough producers in the future to be revived again -- with Sondheim's works being the main exception to that rule. So, we've probably seen the last of "Wonderful Town," "Bells Are Ringing," "Side Show," "Steel Pier," "Jane Eyre," "Sunset Boulevard," "The Wild Party," "Thoroughly Modern Millie" on Broadway.
"What a story........ everything but the bloodhounds snappin' at her rear end." -- Birdie
[http://margochanning.broadwayworld.com/]
"The Devil Be Hittin' Me" -- Whitney