The endosome fuses with the plasma membrane allowing the insulin receptor to re-integrate there. Any degraded insulin remnants which remained in the endosome are also expelled (The majority having been excreted into the cytoplasm and secreted out of the cell via other mechanisms).
The cycle is complete with the dephosphorylated receptor now back in the plasma membrane available to bind the next insulin molecule presented to it. There is some insulin receptor degradation over time when damaged insulin receptors are not recycled but fuse instead with the lysosomes where they are degraded. However the majority of insulin receptors are recycled back to the plasma membrane with greater than 95% efficiency.