Just like the way you can hide your status from specific people you will be able to hide your last seen status from specific contacts.
This comes as WhatsApp announced that it is currently testing the new feature that will let you choose specific people.
Currently, you can hide your ‘last seen’ from (everyone, my contacts or nobody).
The new feature will add ‘My contacts except..’ to the list.
It is currently in Beta for both IOS and Android, it will hopefully be released to all WhatsApp soon.