Even if you run out your RP and will leave after 2 months from its expiration date, you still need an exit permit from your sponsor to leave the country.
UNLESS... like i said, if they reported you to the authority as absconding or run away from sponsor. Then your sponsor is no longer responsible for you but the authority, and the authority will look for you and deport you without the need of exit permit.
Only a small correction here...
Even if you run out your RP and will leave after 2 months from its expiration date, you still need an exit permit from your sponsor to leave the country.
UNLESS... like i said, if they reported you to the authority as absconding or run away from sponsor. Then your sponsor is no longer responsible for you but the authority, and the authority will look for you and deport you without the need of exit permit.