@Bijay305 This will vary depending on the use case for Yammer.
For an organization that is moving all global communications to Yammer, having only a small portion of users using Yammer would be problematic.
But for another org that uses Yammer as a platform for clubs and communities of interest - and doesn't expect everyone in the org to be using Yammer - then having a smaller portion of the userbase on Yammer would not be an issue.
