I would guess that what both Denethor and Faramir were talking about with Boromir is that when it came down to the rubber hitting the road, he would try to take the ring if there was no other way. But that doesn't mean he planned to do so as early as the Council. The Council reveals why he is so blind in his understanding of the ring and why he would think later on that taking it was the only way to save Gondor, and Denethor and Faramir explain more of his character as to why he would be seduced by the ring in such a way, but as to Boromir planning to take the ring by force ahead of time I think there is no real evidence of that. At least, not from these quotes related here.
I think Faramir in particular was seeing that his brother, in the end, would not have been able to resist the lure of the ring because of the way he thought about things and the way he viewed "Isildur's Bane" plus his relationship with "Daddy Dearest."
On the other hand, it is great foreshadowing of what is to come, and I liked how in the movie, Elrond and Gandalf picked up right away on the fact that Boromir's reaction to the ring was indeed a great danger to the success of the quest.
The Council reveals why he is so blind in his understanding of the ring and why he would think later on that taking it was the only way to save Gondor, and Denethor and Faramir explain more of his character as to why he would be seduced by the ring in such a way, Poor Boromir! He has no clue what he's up against! Now the Ring is working on Boromir as well as Frodo. At this time Frodo has been fighting the Ring ever since Gandalf threw it in the fire. The Ring has tried time and again to betray Frodo to the Ringwraiths and nearly succeeded.
Boromir doesn't even know the Ring has already affected him.