If you think that the Geary + GNOME Contacts + GNOME Calendar + GNOME Tasks can handle the enterprise usage, then it's great.
Actually they don't because online accounts doesn't yet have CalDav or CardDav support. Don't think just for gmail users. So the only way I can have all these into Gnome is through Evolution. I don't use it as a client because of UI issues. But Geary & California or even Gnome Calendar & Gnome Contacts sync with evolution-data-server for these kind of data.
So until Online Accounts gets up to speed with Open Standards, I think it would be a step back (in terms of Workstation functionality) to drop Evolution.
~nikos