He wouldn't. Especially since he was bisexual, so if you got his friendship high enough as a male OR female, he was loyal to you to the end even if you chose not to have a relationship with him.
Now YES, there was a way for him to try to kill you again- neat the end game, in Denerim, the Crows would spring a trap for you. His friend Talesan would try to convince him to come back to the Crows, and if his loyalty was too low or you spoke to him too harshly at that point, he would betray you and you would have to kill him.
He mad a more effective combat rogue than Leliana, but you had to manually give him the Lockpick ability because he never learned it. Plus, if you had him maxed out in loalty, were in a relationship with a 'hardened' Leliana, and went with the two of them to meet Isabella at The Pearl in Denerim, you could have an implied Foursome. Little easter eg that had no reward that the developers thought might be fun to throw into the game.