The thing with my SE isn't the 4" display but its form factor / physical size.
If Apple would simply take the iPhone 6/s/7/8 form factor then this is indeed NOT a SE successor!
However,
If they'll get the screen to body ratio and squeeze 4.7" for a similar form factor of current iPhone SE, I guess most SE owners would be happy campers.
I don't agree. With the 4.7" screen I can't reach e.g. the P key an other keys on the right side of the keyboard with my left thumb while holding the device in my left hand. I also can't, for example, focus the URL bar of a browser tab while holding the phone in a normal typing position.
I only have the one hand so don't try to give me advice about how to hold the thing.
Have you seen the option to push the keyboard over to one side? Hold down the keyboard switcher button (you'll need at least two keyboards enabled) and there will be an option to move it over to one side or the other. (Native OS keyboard, iOS 12, I think.)
Also, the "reachability" feature is nice: double-tap (NOT click, just touch) the home button (or swipe down on the little bottom bar for iPhones lacking a home button) and the screen slides down half-way. I can reach the URL bar this way without moving my hand from typing position. (This does have to be enabled in settings.)
Side note: I've often wondered what it would be like to have only one hand to type with. What kind of a keyboard do you use? Any special software, etc.?
Too bad some people can't even reach the keyboard switcher button when holding the phone with one hand. It makes the one-hand options pointless if I need both hands just to activate it. It's now as far to the left of the screen as possible on the X (and above) and I can't reach it with my right thumb when holding the phone normally.
Yes, the hacks that Apple added to work around the fundamental usability problems of the > 4" iPhones do work, but they don't turn them into 4" phones in all respects.
You might want to consider switching to Android which has lots of 3rd party gestures/customization options in general, including browsers with addressbar/tabbar at the bottom.
If Apple would simply take the iPhone 6/s/7/8 form factor then this is indeed NOT a SE successor!
However, If they'll get the screen to body ratio and squeeze 4.7" for a similar form factor of current iPhone SE, I guess most SE owners would be happy campers.