The watch of the future may not get any buttons at all.
The iPhone 7 and 7 Plus do not physically press the home button, but instead use vibration to simulate the effect. The same goes for the MacBook. Now Apple Watch gets the same.
Not sure it will be this year
Apple Watch 4 is expected in September together with three new iPhone models, and now we know one of the news (the source says a 2018 launch is not guaranteed and this can still be postponed to next year):
no physical buttons beyond the digital crown that could still be turned to browse content.
Provides this user benefit?
Instead, they have two buttons, one on the top of the digital crown, and one larger on the side, sensors that notice that one is pushing. This while the Taptic Engine vibrates so the user is aware of the pressures.
This will probably save space for perhaps larger components on the inside and make the clock more waterproof, maybe for a long time.
This is exciting
The source reveals to Fast Company that Apple's Design Group develops a Watch that does not have buttons at all, but that user can tap sites at the side of the clock.
The company evidently also develops the possibility that the buttons on the clock can be used as the sensor source number two, which certain analyzes will need. These are things they can bake in now as the buttons may no longer have physical pressure, but a sensor that is skin-sensitive.
We can not imagine anything but Apple has explored this on the iPhone, too, with a home button that analyzes heart rate.