According to a report on GSMArena, the upcoming device may be "more compact" than the current iPhone 8 Plus. The dimensions of the iPhone X Plus are slightly smaller than the iPhone 8 Plus: 157.2 x 77.1 mm (6.18 x 3.03-inches) compared to 158.4 x 78.1 mm (6.24 x 3.07-inches).
Also leaked is a blueprint for a "budget" iPhone which also looks rather similar to iPhone X, but still has some noticeable differences.
One interesting thing to note here is that the report went on to add that Apple may be bringing the triple cameras to its iPhone series. We expect the third one to be an nearly carbon-copy of the iPhone X with faster internals, Face ID 2.0 and perhaps the same triple camera as the 6.5-inch top of the line iPhone. That being said, the design seems to be a direct copy of the iPhone X, complete with the notch and associated sensors for FaceID. According to Kelly, this is confirmation of a triple-camera setup, just as Huawei introduced with its flagship P20 Pro handset. The phone will have a single rear camera and will also lack the 3D touch feature. All three of this year's new iOS powered handsets should feature the TrueDepth front camera, Face ID and a notch.
So those are two of the projected three iPhones for 2018.
The schematics were obtained by Forbes from accessory maker Ghostek, so they're not necessarily Apple's own schematics, but there's a fair chance Ghostek does have access to design information, since it will need that in order to have cases ready for the launch of the iPhone XI range.