Considering that Keoghan has either shot - or is in the process of shooting - a pretty substantial audition / short movie for it, it's safe to say he's thrown his hat in the ring.
Chris McKay, who's signed on to direct the film, has officially kicked off the audition process and took to Twitter the other day to confirm the news and to offer a few tidbits of advice to any would-be Graysons. While he did confirm that there was an open casting call, McKay stressed that going through an agent was to way to get ahead.
— Barry Keoghan (@BarryKeoghan) November 8, 2017
"An agent or manager protects you and also is an endorsement of your character. It means you take yourself and your career seriously... and so does someone else." As for performance and character, McKay didn't go into specifics or even confirm an age-range for the character, so it's anyone's guess how it goes.
When we spoke to Barry Keoghan a few months ago, the topic of Nightwing came up and he wasn't shy about saying he wanted the role - so here's hoping it works out for him.