Abdu

The author of this article, doesn't seem to know his Metroid lore/timeline, or hasn't paid attention at all.

If they did want to retcon, they would have just named it 'Metroid Beyond' or 'Metroid Prime Beyond' and made sure to drop the '4' from the title to avoid any connection.

Also, Sylux presence and making sure he was prominently in the first trailer, was a clear sign that this is indeed intended to be a continuation.

Sure they can introduce a new direction through MP4 or even end the series in order to retcon, but MP4 is a definitive sequel.

They can add new elements to the gameplay that can be more appealing to attract and excite a new/wider audience, as well as bring something new to existing fans (which they seem to have done by introducing psychic abilities, as opposed to just getting same arsenal again), but as a title, it definitely and clearly is a continuation to what existed before it.

To add to everything you mentioned;

Metroid Prime 4 as a launch title is indeed the perfect showpiece to demonstrate the Switch 2's power difference and technical marvel, when compared to the current Switch.

MP4 would also be the perfect title to demonstrate how the version for the current Switch, would look when played and upscaled on the Switch 2.

Upscaling is a feature Nintendo is surely going to want to demonstrate as a selling point for how Switch titles would upscale when played on Switch 2...not just to impress but to give incentive to current Switch users to upgrade and Switch (pun intended).