You would hope, but my fear is that it's the opposite. That when mastectomy fails to relieve dysphoria as expected, phalloplasty is the next target. Similar to how the goal constantly shifts for someone with an eating disorder ("if I weigh X kg I'll be happy" where X = X-1), the experience of dysphoria could be similar - first binding, then blockers and hormones, then mastectomy and finally phalloplasty?
This makes sense to me - at least for people who have a deep unhappiness with the self that they seek a resolution for. My trans-identifying relative definitely follows a pattern of increasing "transness", which appears to be an extension of a previous pattern of seeking diagnoses and identities over many years. With each new revelation/diagnosis/identity they announce they are happy and finally at peace with who they are etc. It lasts a year or so and then they take the next step further.
I once suggested to them that they might change their mind about something, and got a massive bollocking, how dare I suggest that, they knew themselves best and would not change their mind. Well, they didn't change it back, but they did change it from "they", to "he" and then to going on T. That of course is fine, as long as you are becoming more trans, you're discovering your true self.