Why it won't last forever

? 40 sat/byte that would be 0.6$/per transaction if I'm correct...Are we going to see transactions that cost 10$-50$ and barely gets confirmed again like last year

?
I think you just answered your own question: block space is still limited, and whenever blocks are full, fees can skyrocket again.
Especially since the most bitcoin users have some sort of one-up mentality regarding fees, causing them to spiral extremely quickly.
It's not only the users, the wallets they use contribute too. If you combine those two,
uninformed users cause high fees, and that's one of the reasons I opened this topic.
The Lightning Network is great for micro-payments since its transactions are instant and cheap.
I can't wait to use it indeed!