What is the upgrade path than?
If you want to keep your company On premises Exchange Server for hybrid deployment as not confident on pure cloud services. You can upgrade to Office 365 Enterprise E1, then data still can keep on your server and on the cloud.
If you want to combine Office 365 Business Essentials together with Office 365 Business to include Microsoft Office like Word, Excel, PowerPoint, OneNote, Publisher, etc. Then your company can upgrade to Office 365 Buisness Premium.