This is the answer to Will Google Wave be a success?

Yes, because it makes communication more organized

Everyone uses email and it always turns into a mess. Especially if there are many people involved, it's difficult to keep track of all the replies-to-replies-to-replies.

Google Wave's editing functionality will solve this because it means people can update old 'emails' instead of creating new ones. Much more concise.

The instant messaging function will also be great. Communication will no longer be needlessly split between two completely different application. This is convenient for accessing old communication and generally keeping things organized and accessible.

The overall effect is that Google Wave will make things faster, so people who keep to "email 1.0" will be left behind.