Jonas was discussing the possibility of his disappearance with the Giver. Was the Giver upset by this discussion? Why or why not?

Before Jonas came into his life, The Giver accepted things
the way they were.  He knew that what the community was doing was wrong, especially
after his former Receiver Rosemary committed suicide.  Jonas might have gone along with
the ways things had always been too if he had not had Gabriel’s influence.  Although
Gabriel was only a baby, he gave Jonas the opportunity to have a relationship with
someone condemned to be Released.

Notice that The Giver
never makes an effort to stop Jonas’s plan.  When he is harsh with Jonas after his
violent reaction to the murder of the newborn twin, it is because he needs Jonas to
understand that no one is evil in the community but they simply do not know better. 
Jonas can never look at the community the same way, and he and The Giver plan his escape
with Gabriel as soon as Jonas learns Gabriel is going to be
killed.

I think you can infer that The Giver even becomes a
little excited about the possibility of change in the community.  He agrees to stay
behind and help the people when the flood of memories return, because he knows they will
need him.