I think you are overestimating it. Do you think they will also keep printing the 2014 books? I see no difference there
People who want the 2014 books in physical will still be able to get existing and unsold or second-hand copies, very easily.
With Beyond, though, you'll have a gigantic problem. Your only option will be to convince someone who has the 2014 stuff to "share" it with you, but given you can what, only share with three groups, that's very limited, and further it relies on that person staying subscribed.
where did they promise that?
They've said several times that they wouldn't take stuff away, and that 2024 isn't a required change, nor an edition change, it's just new stuff you can take or leave, and most importantly, with race/class changes, they've relied on this as a defense, saying "If you don't like it, you can always just use the 2014 version!".
If they take away new access to the 2014 version, that will not be true.
gamers won’t care, those who wanted to get into D&D would go with 2024 anyway. No new player will buy the 2014 version
LOL. This is just unrealistic and silly. Gamers absolutely will care - even people who don't currently play D&D will be mad about it. And this idea that people will never want the 2014 version is just laughable, because I guarantee, based on the playtest, certain classes/races/spells will either be better in the 2014 version, different in interesting ways, or only exist in the 2014 version, and that will ensure people care and want to obtain the 2014 version.