I'm not sure I understand, it does exist, it's called
Ligamentolysis. If you meant to ask or say will there ever be a procedure that guarantees
Erect length, well then that would be more aptly put.
When considering length, you'll have to appreciate the challenges posed by our anatomy to understand why length gains are much harder to come by than
Girth gains. Length is possible with the aforementioned ligament-severing procedure, but I understand the frustration of not being able to determine if (1) any gains are guaranteed, and (2) the extent of those gains.
Hopefully either
Ligamentolysis improves through some innovative technique or a new procedure altogether surfaces. My guess is that stem-cell advancements will be the future of
Phalloplasty, when the science is so common that elective medicine can employ its benefits. That said, the current methods are viable (especially for
Girth), and if you're under-average in length,
Ligamentolysis performed by an experienced surgeon is worth consideration.