While it's sad that Attack the Block didn't do well, I don't think it's hurting Joe Cornish's career. I believe this is an example of a movie where studio execs can look at it, can get it and will want to give him more work.
Case in point! Paramount has hired Cornish to direct an adaptation of Snow Crash, one of the most important modern scifi books. Neal Stephenson's novel was named by Time one of the 100 best English-language novels since 1923, and its cyberpunk trappings - while seen by some as satirical - informs much of current science fiction. It's also a really good book.
Paramount has had Snow Crash for a while, and at one point the guy who wrote The Day After Tomorrow would adapt it while the guy who directed Demolition Man would direct. That certainly would have been an interesting take on the material, which some believe is essentially unfilmable.
Bringing in Cornish is exciting for a number of reasons, not the least of which is that I like the guy's first movie so damn much. But his style and his thought process will be fascinating when placed against Stephenson's often-strange book. Should this movie go ahead - and that's a big should - I think it has a chance of being great.
I think Deadline's synopsis (probably taken word for word from a Paramount statement) is a fine surface level summation of the story:
The book is set in the near future, when the U.S. exists as a patchwork of corporate-franchise city-states, and private enterprise and the mafia control everything. The plot involves a computer virus that is manifested as a drug called Snow Crash that is transmitted visually from computer screens to unsuspecting users, frying their brains. Hiro Protagonist – that’s the character’s name – a computer hacker/samurai swordsman/pizza delivery driver who investigates and tries to stop the takeover of postmodern civilization.
But you should definitely read the actual book as soon as possible.