How real is the iPhone 5se? Or the iPad Air 3? Real enough that Chinese case manufacturers already have products (or at least mockups) to sell. At iPhone Life, we received a press release from at least one firm with prices and photos for its iPhone 5se and iPad Air 3 cases. The photos are reproduced here, and seem to indicate that the iPhone 5se will resemble the flat-edged iPhone 5 on the sides, but with the rounded bottom of the iPhone 6 series. The iPad Air 3 case doesn't look that different from the iPad Air 2. The case appears to have large openings on the outside, as the next tablet is expected to have four speakers, like the iPad Pro.
Any retailers thinking of ordering these need to keep in mind that these mockups are based on rumored product features or actual leaked designs. It's probably safer to wait for the official product to get a case made with reliable measurements and not just on speculation.