Battlefield 1 has been officially announced by EA and according to Gamespot, the latest press release has vague details on the public beta coming later this year.
You can sign up for the Battlefield Insider program here, which is a subscription to EA’s newsletter. According to the Insider site, perks included with the newsletter signup are access to the beta, in-game rewards, exclusive content, and a “sneak peek at news about Battlefield.”
Battlefield 1‘s tentative release date is October 21st, so I would assume the beta will probably run around late July – mid August to allow for any flaws and data to be collected in time to make changes before the game goes gold.
There doesn’t seem to be any indication that this is a limited signup or end date for this Insider program. I would recommend if you are interested in checking out the beta when released, then jump on this as soon as you can!