Does trading steam game gift active immediately?

Hi all, I have been inactive for quite a while from steam.

Recently, I trade a game and I have to wait for 15 days. The trade is ongoing and still counting to 15 days.
If I decide to buy the game within this period of 15 days, what happens after my trade is completed?
Will I still receive the game in gift form in my inventory, or is it need to be activated immediately (in this case rejected because I already own the game)?

I am not familiar with the new steam trade system, please help.