Hmm, it's always tricky when talking about semantics.
Gender dysphoria is a specific condition that is defined in the DSM-V. It can be cured, and once it is cured, it is gone.
'Transgender' usually refers to a person whose sex assigned at birth does not match their experienced gender. So, in my opinion, which means nothing at all in the grand scheme of things, one would still be trans even after a successful transition.
At some happy time in the future, I will feel no dysphoria. I will feel fully female and will be experienced by others as female. My transition will be over. But in my history, I will always have been assigned male at birth. So, I think I would still be trans.