In the seasons so far, we have only seen three giants, and now they are all dead. Will we see anymore in the future, especially since the great war with the White walkers hasn't occurred yet?
This is open to speculation:
Wun Wun was a Giant, possibly the only one to reside in Hardhome and possibly the last giant to ever be seen on the show
In the books, his fate is unknown too, but he is in confrontation with Stannis' knights:
[Jon] hears a commotion at Hardin’s Tower. He rushes there and sees Wun Wun smashing the head of a knight named Ser Patrek of King’s Mountain... One foolish man shoots the giant in the back with a crossbow, and in retaliation Wun Wun grabs the man by the leg and whips him into the wall
This happens just before the close of the last published book.
Source: gameofthrones.wikia. Emphasis and editing is mine