The future of the Group of Eight depends on Russia, and Russia needs the G8.

If the other members decide to expel Russia, the G8 will simply cease to exist for Russia. In fact, it would be a blow for the entire organization. International organizations can cease to exist for many different reasons. One is that their agendas become completely trivialized. For examples you need only recall the meaningless international organizations Russia belongs to. Another is that they can be expanded to such a size that no problem can be discussed productively. If you were to include China, India, Brazil and other countries in the G8, you might as well call it the "UN Without the Small Countries."