To be clear, there isn't an exact release date for Apple's next set of iPhones. But, it appears that some things are starting to solidify when it comes to the design if the latest batch of leaks are to be believed. The latest render is from the accessory site, Mobile Fun, and is a product that is apparently coming from Olixar.
The screen protector looks to be available for purchase and judging from the design, it looks to be based on the iPhone renders we have been seeing over the past few weeks. Naturally, things could always change, but it would be a fairly risky gamble for an accessory manufacturer to produce a product without prior knowledge of device compatibility. There are always variances, so there could be a refinement of the product once the handset is closer to launch, but this could be close to what will arrive to retail.
The screen protector looks like your standard product offering up, with the following description on the website:
"This ultra-thin full cover curved tempered glass screen protector for the iPhone 8 from Olixar offers toughness, high visibility and sensitivity all in one package. Features complete edge to edge screen protection for black phones."
As mentioned before, there hasn't been an announcement from Apple about an event, so there is no timeline as to when the next iPhone will arrive.