I don’t think so.
While RingCentral is certainly a very interesting company, with $300m+ in revenues … it’s too downmarket.
Salesforce has made a series of material acquisitions that are more SMB-y … ExactTarget for $2.Xb for sure, and even SteelBrick recently is more “downmarket” than say Apttus. RelateIQ’s customers were smaller tech companies, for the most part.
But very small businesses is, I think, one step too far downmarket for Salesforce.

Awesome problem to think about. I have been involved in Contact Center infrastructure and lately Sales Acceleration applications.
There is one scenario where RingCentral acquisition by SFDC might make sense. If SFDC as a strategy wants to get to “all desks” (Horizontal) in a organization and take microsoft Unified communications head-on then I believe Ringcentral makes a good choice. This may not necessarily be a downmarket strategy in that case.
Ringcentral does not have a strong vertical applications portfolio and if the goal of the strategy is just to go down market then infusionsoft / Zoho would have made better choices (Hypothetically 🙂 )
My 2 Cents 🙂
-Sachin
Founder Inside Sales Box