This is my concern as well (+ I'm a cheapskate who usually only buys consoles or computer stuff once they're pretty much obsolete and <$100 used).

History of every gaming device I've bought in adulthood including VR:

1. Purchase with some games;
2. If soft-modable, soft-mod and customize;
3. Play happily for a few months;
4. Put it in a box and never look at it again, or give to my kid who follows a similar cycle.

Edit: Though my counterargument here is just how many options the Steam Deck opens up. Want PC games - see: all the shit I've never played? Got 'em. Emulators? Got em. Want to use it as a mini pc for minor pc stuff? Doable.