The SE is a completely different market and it won't consume iPhone 8 sales, because Apple is not going to give it all the latest features and capabilities of the iPhone 8. It's likely going to adopt a lot of the iPhone 7 features. Not To mention, the smaller form factor of the iPhone SE is a very small percentage of iPhone users that actually want that specific type of device.
Reason I mentioned the SE2 is not necessarily the form factor but the screen size in conjunction with true bonafied 1 hand / 1 thumb usage. Yea even if the SE2 does get a full edge to edge LCD screen it still might be too small of a screen after looking at the specs of the current SE.
The non Plus iPhone has been notably recognized as a true 1 handed device that can even be used with 1 thumb without any hitches for most people.
For me this is why I much prefer the non Plus 6/7/8 and believe it or not the bezels and the home button help. When I had the X reachability I had to swipe further down on the screen and often times had to try more than once to get it to work because of it being an inconvenient place for 1 hand use. I do use reachability a lot on my 8 and I can access it on the home button without any inconvenience or adjusting. I’m right handed and my right thumb can easily reach the top of the 8 screen to access notifications and my thumb can easily access Control Center which I use a lot from the bottom. Accessing the CC on the bottom isn’t accessing it on the bottom of the device itself but the screen which has a home button and bezel underneath.
My 8 is in a Magpul case and I can literally hold it in my right hand and navigate all over the place like it’s part of my hand on my pinky shelf while my fingers are holding the device against my palm.
That’s just some experiences. I was thinking of the SE2 was edge to edge in a smaller form factor it would help with convenience.