The upcoming Guilty Gear Strive crossplay beta has been pushed back by a couple of weeks. Said test was originally slated to begin in mid-September, but Arc System Works says it's now slated to arrive in late September to early October, so you'll have to wait a bit longer for it.
Why has the Guilty Gear Strive crossplay beta been delayed?
In a Developer's Backyard post, game director Akira Katano explains the reason for this Guilty Gear Strive crossplay beta delay. According to Katano, "unexpected delays" in readying the game's test client have resulted in a delay to the beta test, so it's now scheduled for "late September into early October". You can expect details on how to join the test to appear on the Guilty Gear Strive website at a later date.
It's not all bad news if you're a Guilty Gear Strive fan and you want to play with your friends, though. Katano also says that the team is looking into allowing "anyone to join [the crossplay beta test] for free", even those who don't have the game. If there's someone you've been meaning to introduce Guilty Gear Strive to, this could be the perfect chance to do so.

Once the beta test is complete, crossplay will release after some "final adjustments". Arc System Works says it's currently hoping to do so sometime during fall 2022, so it hopefully shouldn't be much longer before you can fight your friends in Guilty Gear Strive no matter what platform they're on. More updates should be forthcoming soon, so keep an eye on Guilty Gear Strive's socials for further updates.
What is Guilty Gear Strive?
Guilty Gear Strive is the seventh main game in the Guilty Gear series (although it's far from the seventh game in the overall franchise). Arc System Works has said the game is intended to be a "complete reconstruction" of the franchise, and other staffers have said it's intended for both new players and returning players to enjoy. This strategy seems to have worked, given that Guilty Gear Strive sales crossed the million mark recently.
The success of Guilty Gear Strive has led to numerous characters being added as DLC, including most recent addition Bridget, who the above Developer's Backyard post also confirms as trans, saying she "self-identifies as a woman". The modding scene for the game is, as you would expect, thriving as well, with mods mixing in everything from Granblue Fantasy Versus through to Dragon Ball FighterZ.

You can pick up Guilty Gear Strive right now on PC and PlayStation consoles.