Forumite Palodin has pointed us to a tweet by SOE president John Smedley explaining that the Planetside 2 beta keys given away by PC Gamer US in April and UK in July will be activated "on Friday by 5pm" - that's today. He presumably means 5pm PST, which is 1am GMT on Saturday.
We currently do not know if all of the keys will go out at once or if there'll be another wave after today. However, if you haven't redeemed your PS2 code yet now is the time to do so. We're currently working through the remaining support e-mails - if you've requested a code, expect it within the next hour or so.
We've asked SOE to confirm whether or not the PC Gamer codes will continue to be valid after today. Until we receive a response we advise people not to buy issue 241 solely for the purpose of obtaining Planetside 2 access. There are plenty of other reasons to buy it, of course, but we can't currently guarantee that the beta codes will still be valid.