Bo Xilai's expulsion from the Party is very significant indeed. In contrast Deng Xiaoping retained his Party membership over 3 removals from office allowing for 3 comebacks to power. Bo will likely never be seen in public again.
It suggests that Bo will become the focus of a major Party-wide campaign. This has been the norm for high-profile people expelled from the Party in the past. Expulsion of senior officials from the Party is a very serious and very rare political event. The fact that the Xinhua news release says Bo will be up for abuse of power and bribery suggests the possibility of very far reaching implications for others who are engaged in comparable corrupt practices.
So I take his expulsion as a promising development that could indicate that the 18th Party Congress may adopt meaningful reforms to bolster the Party's battered reputation with people in China and abroad.
Obviously it will infuriate many powerful people who will be exposed to serious charges. But the Party appears to be willing to risk instability instead of the continuing stagnation incurred by doing nothing meaningful and therefore suffering continuing corrosion of its legitimacy in the eyes of the people.