The superhero sequel engine is revving up bigtime.

Warner Bros. Pictures is already planning the next installments to "Batman Begins" and "Superman Returns," with respective helmers Christopher Nolan and Bryan Singer in line to return.

Neither director's deal is closed; the studio has hired Jonah Nolan -- Christopher's brother -- to pen the screenplay for the untitled "Batman" project. Studio has options on "Batman Begins" star Christian Bale and "Superman Returns" star Brandon Routh.

Next installment in the Caped Crusader franchise is further along in the process since "Batman Begins" was released last summer; Singer's "Superman Returns," now in post, doesn't bow until June 30.

Legendary Pictures, which put up half the financing for both "Batman Begins" and "Superman Returns," is expected to board the sequels and split the budgets 50/50 with Warner Bros. In return, Legendary would split all profits, also 50/50.

The Warners-based Legendary, led by Thomas Tull, is a financing and development company backed by more than $500 million in private equity.

Projects come as no surprise considering Warner's proclivity for big-budget tentpoles. "Batman" and "Superman" sequels could make their debut in 2008 and 2009, respectively.

"Superman" update, which has been in the works for the better part of a decade, is already considered one of the more costly pics in Hollywood history, although Warner Bros.' exposure is dramatically lessened by Legendary's involvement.

Factoring in tax breaks offered in Australia -- where "Superman Returns" was shot -- studio execs have unofficially put the production budget at $185 million. Without those breaks of about 12%, budget is easily north of $200 million. And it's not clear how much previous commitments have cost the studio.

Warner execs are high on Singer's pic, which returns the comicbook hero to the bigscreen after more than 20 years. Traditionally, Superman has enjoyed wider appeal than the grittier Batman.

Nolan's "Batman" took in $205.3 million in the U.S. and $166.5 million overseas.

One idea being tossed about is for Singer to direct a "Superman" sequel soon after he finishes with Warner's remake of sci-fi thriller "Logan's Run," which he's also expected to direct.

"Logan's Run" is tentatively skedded to begin shooting this fall in Vancouver. If Singer did pact to direct the "Superman" sequel, that pic could be shot in Vancouver as well.

Singer is also set to direct "The Mayor of Castro Street," which is in development at Warner Bros.

It's not clear when the "Batman Begins" sequel would begin shooting, although it would likely start production and be released before the "Superman" sequel.

Christopher Nolan is presently shooting "The Prestige," a Disney release that Jonah Nolan scripted from a Christopher Priest novel.

"Batman Begins" co-writers David Goyer and Christopher Nolan wrote a treatment for the sequel. Goyer, who recently completed "The Invisible" for Touchstone, also is set to write and direct "The Flash" for Warners.

(Ted Johnson contributed to this report.)

Contact Pamela McClintock at pamela.mcclintock@variety.com