Cheating someone certainly is, not doing whatyou said you would do in the agreement is, but not telling someone whatyouintendtodo as a result of the agreement is not.
But, ultimately, part of being principled, part of being a leader is, A, being able to describe exactly what it is that youintendtodo -- not just saying I'll sit down, you have to have a plan.
If you haven't done this yet, Mr. McCusker recommends doing so several months prior to announcing your desire to split up to avoid letting on whatyouintendtodo.