uhoh roland i'm gonna ruin your day. it depends on the leader, some are guaranteed safe at pleased, as long as they stay pleased. they all have a rating for "war pleased". safest is 0/100, means they won't declare on you at pleased*. that's folks like gandhi and hatty. the worst is 20/100, that's folks like monty (surprise surprise) and cathy. hubby looked up gilgamesh for me in the stickied .pdf when i saw this thread, gilga's a 10.
this factor i'm talking about is for their own RNG decision to declare war on you. there are different factors for whether somebody else can bribe them into war with you, so some might not be guaranteed safe that way, i don't know those numbers. and with BtS, there's the extra added fun of holy wars, where if you're the wrong religion you could in theory have 8 civs declare on you during the same turn, 3 of which are at friendly

!
*technically, they won't
decide to declare on you at pleased. but if they made the decision before you reached pleased status, and they're still preparing for the war, then they don't change their decision just because your relationship gets better.