Some art styles are so strong, they define an era, but as time moves on, the art style may become trapped as an element of the past and look old—even in new productions. (To see evidence of this phenomenon, check out any of the recent projects based upon Tezuka Osamu's Manga). Additionally, animation techniques constantly develop and make old animation motion look rough and stilted. The color of the characters has become more vibrant, the quality of the animation direction has become more dynamic (at least in the good shows), and the soundtracks continually reflect the current era of musical tastes. Unlike live action films which rely upon the actors and their acting ability for their life cycle, there are many more aspects of animated projects that can show their age.
For example, when I think of Humprey Bogart, I do think of black and white films (old production values), but I also think of him as an excellent actor and that I will find entertainment value associated with his projects. CASABLANCA, SABRINA, and TREASURE OF THE SIERRA MADRES are examples of the films that reinforce my feelings and make me a fan of his work. However, since he is an actor, he is timeless. While fashions may endanger the look of a live action film, many of Bogart's films don't suffer as much—Khaki's and Tuxedo's seem to be classic styles in their own right. Bogart's face is not an art style, and his acting is both real and convincing.
Unfortunately, this is not always the case for animated projects. Some animation art styles seem dated because they are only associated with older animation projects in which the production values suffer from the standards of the time. Maybe the key to the survival of these properties is to remake selective projects (animation or even video games) with updated production values to eliminate the "old" stigma. For example, despite my appreciation for Matsumoto Leiji's place in Animation and Manga history, his art style has little appeal to me and I associate it only with old projects in which I have no interest such as YAMATO or GALAXY EXPRESS 999. So when I see that they are releasing a new EMERELDAS OVA, I think "Oh, another Matsumoto project. Looks old." This is equivalent to "Oh, that Bogart dude, he did stuff in black and white. He's dead now." I must admit that my interest levels have prevented me from giving the project a chance, and perhaps if I ever see the title I will be dazzled by the amazing production values, the sweeping drama, and the strong characters. Perhaps then, I will become a fan who has a deeper appreciation for Matsumoto and who will be able to seek out the older projects with fresh eyes—and perhaps not.
To Tezuka's credit, his simple character designs make his characters very accessible, but on the other hand, most of the recent projects associated with his name have done very little to dispel the "old" connotations from his name. KIMBA and ASTRO BOY are only available to me in their simplified dubbed versions, and without any nostalgia for these titles, I don't find them interesting in the least. My wife was a big fan of the BLACK JACK manga, so the animated version was my last hope to catch a glimpse of what made Tezuka the Icon that he is. Unfortunately, I only caught the barest glimpse. With the exception of only one episode, I found BLACK JACK to be stilted, overly dramatic, and boring. Fortunately, I have since been able to read Tezuka's ADOLPH and recognize his significance, but it is a sad day when a manga set in World War II seems more timeless than his animated projects—

Orpheus was formulating the response to the first question, but was briefly distracted by new arrivals on the Stygian shores. The girl in the Tiger Bikini was sexy and electrifying, and that Madoka chick could play a mean sax, but he quickly shook off their charms and concentrated on the love that was deepest in his heart.

Financially, there is less and less incentive to dust off classic shows whose value may lie more in nostalgia than reality when stacked against their competition. This is where pride plays its part. If the creator or rights holder values nostalgia, their investment, and their prestige above the need to expose an audience to their property, the price for licensing may exceed the interest of potential suitors. However, for these business oriented organizations, retaining the product as a high priced possibility may still make more sense (in the form of the almighty "on-paper" dollars) than as a small amount of real cash.
So, is it possible for the rights holders of classic titles to tempt a potential licensor? Certainly, but it is an uphill battle both for the licensor trying to get the highest value for their property, but also for the licensee who must sell the product to the public.

Orpheus reflected upon the loves of his life and what made each one special, and, in particular, what made Fujiko so special. Certainly her fire, her energy, her shameless larceny and the way she filled out those dresses made her a classic babe. The fact that she was getting a bit old for others to appreciate her values only made him cherish her more! Surely there were plenty of reasons to extract her from Tartarus so they could continue their relationship?

Only the very best projects achieve a real timeless nature. Walt Disney's SNOW WHITE, for example, is only dated by the style of the song vocals and voice acting. Since Disney's art style or techniques didn't change very much over the sixty years that follow SNOW WHITE, it can compare favorably, if not supercede many of the animated efforts that followed it. THE RESCUERS, 101 DALMATIANS, and THE BLACK CAULDRON are examples of more recent efforts that don't really challenge SNOW WHITE's production quality and entertainment value.
From my perspective (and you are both welcome to, and encouraged to find your own), AKIRA and most of Miyazaki Hayao's films are the stand-out animation projects that have the best chance to be considered classics 60 years from now. As much as I love LUPIN III, MAISON IKKOKU, PATLABOR, and GALL FORCE, there are strong elements in these projects (with the spectacular exception of LUPIN III: CASTLE OF CAGLIOSTRO) that date them.