Ann: Autodesk, Inc. Acquisition Proposal (Rejected), page-150

I am not sure that fully cloud-based engineering design packages are as attractive as desktop based in the current environment.
Cloud based sharing on internal servers are more common.
My experience is that there are two inhibiting factors that cause design firms to shy away from cloud-based platforms.
1) security of data - most if not all NDA between design firms and clients as well as sub-subcontractors stipulate strong protection of data and often this means siloing in private domains or even physical servers on-site. Most=often there is a destroy-retained-data exit clause for sub-contractors providing CAD design.
2) speed of operation - when designing in CAD there is a significant impact from the delay using a cloud or even a local server device for running 3D CAD the software because of the intensive nature of the processing for graphics, rendering and analysis functions.

The cloud-based packages have evolved a lot but not yet to the point where they really compete with the "grunt" of a top-end desktop or workstation.
Altium has provided an integration that uses 3D models that are compatible with Mechanical CAD and therefore provide a wholistic design interface.
IMHO it will take some significant work by a company to get both electronics and mechanical parts of the design system fully cloud based in a competitive format.