Crossgrade from Cubase to Nuendo


I am a user of Cubase Pro 8 but since I have recently gotten more into sound design for games and movies I am planning switching over to Nuendo 7 when it comes out. I would like to ask that is there going to be a possiblity to crossgrade from Cubase to Nuendo at some point in the future, or is the only way just to flat out buy Nuendo 7 full version?