I am buying Booking Calendar paid version. Do I need to make future updates from WordPress directory?

No, you do not need to make update from WordPress directory, because then you will use Booking Calendar Free version.
We will send to you update(s) of your Booking Calendar version (if these update(s) are ready) by email directly, after you are request update at this page.
You can check according new updates at this page.
You can receive free updates during 1 year after purchasing of your version. After this 1 year, you can prolong this period for next 1 year of getting updates and support for the 50% of original cost of your plugin version.