Hi Kingbekir,
I publish a new asset pack every month, so yeah, if you want to be up to date with the latest releases new asset packs have to be bought independently. Another option is to be subscribed to Minifantasy's Patreon to receive it as part of your Patron benefits.
The complete bundle increases gradually its price every few months to keep always the discount it offers between 70-75% of the total price of the collection.