Let the Bat Mania begin. Now that Joel Schumacher (Falling Down) has replaced Tim Burton at the helm of Batman 3, what can fans of the $800 million-grossing global franchise expect of the next caped crusade? Some predictions... *An end to the batlash: Hiring Schumacher to direct the summer-of-'95 release is seen by insiders as an attempt by Warner Bros. to get the Batman movies back on track. The studio, which declined to comment, has always given Burton full credit for reviving and modernizing Batman, and Burton's office confirms he will executive-produce the next film. Still, Warner doesn't want a repeat of the macabre 1992 sequel, Batman Returns, which frightened small children and angered many parents. And even though it earned $163 million in the U.S. and Canada, Returns made substantially less than 1989's Batman, which grossed $251 million. ''Warner Bros. didn't want Tim to direct,'' says a source close to the project. ''He's too dark and odd for them.'' Schumacher, on the other hand, has a penchant for making stylish and successful movies out of such moribund topics as vampires (The Lost Boys) and near-death experiences (Flatliners). *Bat in the saddle: Not only does Schumacher have Burton's blessing (''I wouldn't have approached it if Tim wasn't supportive of the idea,'' he says), but he has Michael Keaton's as well. ''Schumacher can make Batman sexier and more heroic,'' says Harry Colomby, a partner in Keaton's production company. ''Burton is not the hero type. His heart beats for the outsider-look at Edward Scissorhands.'' Keaton, who made $5 million for Batman and $10 million for the sequel, could earn as much as $15 million this time out of the Batcave. ''The predisposition for Michael is always to do Batman,'' says Colomby. Also watch for Keaton, who had to share the spotlight with those cute penguins in Batman Returns, to be more of a player in the next installment. And he may wear a new flexible batsuit to allow the Dark Knight more mobility. *New terrors for Gotham City: Schumacher acknowledges that the nemesis probably will be the Riddler, though he adds that it's too early to say whether Robin Williams will play him. (Williams' agent insists no one has contacted the actor about the role.) If Williams doesn't sign on, John Malkovich, who played a menace to society in In the Line of Fire, is the odds- on pick. *Holy sidekicks: Schumacher is toying with the idea of reinstating Robin the Boy Wonder. ''Tim was thinking of having a black Robin,'' says the director, ''but I'm not sure there is going to be a Robin, let alone what race he might be.'' And, of course, Batman will need a love interest. ''There may be a new heroine,'' says Schumacher, though it won't be Kim Basinger's Vicki Vale. ''Maybe some character from the comic books, or it may be somebody completely new.'' *But no cat: Although Michelle Pfeiffer is sitting out Batman 3, Burton and Warner might revive her kitty-with-a-bullwhip in a spin-off. ''The Catwoman movie is just a whole new concept, completely open for Tim's creative vision,'' says Burton's spokeswoman. Adds Pfeiffer: ''I would love to do it. Catwoman breaks just about every taboo.'' *Meanwhile, Schumacher expects to see a script, possibly by writers Lee and Janet Batchler (CBS' The Equalizer), later this year. ''Sure (it's pressure), but that's part of the challenge too,'' says Schumacher, who starts shooting next September. ''This is a wonderful period in the movie's production, where everything seems possible.''