Q. I'm using a 3rd party disk encryption technology. Can I just perform an in-place upgrade to Windows 10?
A. Typically no as the encryption will interfere with the WinRE and new image phases of the upgrade. You would need to disable the 3rd party encryption prior to the upgrade and this would also apply to upgrades between Windows 10 versions. If you are performing the upgrade in a corporate environment the disablement of the 3rd party disk encryption could be done as part of a task sequence (if using Configuration Manager) and then enabled again post upgrade but you would not be able to use the simple upgrade process.
Note that if you use BitLocker (which is also part of professional in Windows 10) this is not an issue and will be handled automatically.