This Is How A Great Handheld Is Created - AYANEO 2S & GEEK 1S Launch Event… - AYANEO (about 3/4 of the way down).
Ayaneo make Steam Deck, Switch like gaming PC’s. They have decided the next major iteration of their product will have the same motherboard layout as they’re previously used and to offer a ‘service’ (no word on DIY kit) to upgrade. On top of that they are planning external enclosures which can house the old motherboards (and presumably the newer ones) and turn it into a mini desktop PC.
Where have I heard all this before? 
Still waiting on that Cooler Master case…