>>211360472
Yes he is a replicant
The original theater version takes out the Unicorn scene, so Gaff leaving the origami unicorn for Deckard at the end seems arbitrary, but Ridley put the Unicorn scene back in the Directors cut, showing Gaff knows Deckard is a replicant, also Gaff says at the end "You have done a man's job, sir".

Deckard is a replicant. So was Tyrell. Batty was originally going to find the dead body of the human Tyrell in a burial chamber in the Tyrell building after he killed the replicant Tyrell, but Ridley was unable to film it.