OnePlus 7 is expected to launch in a few months if we take the company's recent product launch cycle into consideration. The OP 7T is expected to launch in the second quarter of 2019 and it seems like the company is about to adopt a brave new design for OnePlus smartphones. We've seen something similar with the OPPO Find X before and it seems like OnePlus may implement something similar.
It may seem too soon for a OnePlus leak; however a previous leak suggests the same design choice when an image leaked a concept phone in a protective case.February 13, 2019
The leak came from a twitter account that has no previous record of accurate rumours and cannot be verified at the moment. The account does not explain the origin of the image, which makes the leak a bit sceptical. The image in the tweet, however, is in line with a previous leak where the device does not have a notch or even a punch-hole selfie camera. This implies that the smartphone may use a sliding mechanism similar to what you have seen on the OPPO Find X. OPPO, Vivo and OnePlus are owned by the same holding company i.e. BBK Electronics which makes this claim a bit plausible. Vivo and OPPO both launched a smartphone with a sliding mechanism or a pop-out camera last year. So it doesn't seem far-fetched that OnePlus may borrow the same design from its sister companies.
What remains to be seen is the durability of a sliding mechanism and phones in the past have been known to wear down with use. It's a problem with any smartphone that has moving parts which make this a brave design choice for OnePlus if this rumour is to be believed.
From the image above we can see clearly that the device has a noticeable bezel possibly because of the sliding mechanism. It seems to be thicker than the rest of the phone which is very reminiscent of the OPPO Find X.
Since this is a rumour based on an unverified tweet, the picture cannot be corroborated at the moment. We will know more about the smartphone closer to its launch but for now, this leak should be met with scepticism.