In the grammar sections of my textbook, I learnt that
SENTENCE + ことになる
Expresses that SENTENCE has been decided.
However, in this context, it seems more like ことになる indicates that there is/was a change of state.
"If we can all lead a happy life this way, it will be that I have achieved my goal."
If I regard なります as representing present tense, then I could imagine the "decision" semantics working to a degree, but it would make less sense:
"If wen can all lead a happy life this way, I decide that I have achieved my goal."
Again, since my textbook only taught me that ことになる expresses a decision, I wanted to ask for clarification/confirmation in this case.