It's not the price of Windows that was keeping people from adopting Windows 8. It's the irrelevancy and the fact that corporations don't see the ROI. The time it would take to upgrade their company isn't worth the gains, which are minimal. Unless Windows 10 proves to be a massive improvement in performance or usability, I suspect it's uptake will be just as anemic, free or not.
If they're a small business and use OEM installed copies of Windows and those OEM copies are Pro or lower then, yes, they get a free upgrade.
If it comes with Enterprise OEM they won't get the upgrade, and if they are on a volume licence (which most companies, even medium sized are) then they won't get a free upgrade and will instead need Software Assurance (subscription upgrades).
Many companies upgrade because of non-obvious benefits, namely how newer versions of Windows ineract with Active Directory, WDS, WUS, and similar. Every version of Windows comes with new and sometimes impressive enterprise features that consumers just rarely notice.
For example, go here[0] and look at the Enterprise column. It is these types of things that are what gets enterprise excited, not how pretty alt-tab looks or if it has Cortana.