Microsoft Teams meetings and calling news roundup: The latest features and new upgrade tools

I'll be honest, Skype for business has been a bit of failure for most clients i have spoken to where they use the app for instant messaging. Many have reverted back to Skype and deleted Skype for business. This is on the IM side where a lot of business is performed on stock offers and deals are made. Skype for business linked up with appointments in their diary and showed them offline or unavailable, when infact they were present, but had a diary invite to one of their own personal having a day off. Skype for business would not accept any incoming messages and they lost business as they were unaware of this. 
With the forced upgrades on Skype and the move to Team we have alot of clients who use Skype for IM to communicate across language barriers and do business - very worried about the updates. Sadly it feels like MS have decided to upgrade to what they believe is the right thing rather than checking with the users who rely on IM for a high % of their business communications.
My questions are, is Team effectively a name change from Skype but the nuts and bolts remain the same on IM? Or is it something completely new and IM will be majorly affected?