Windows 10 - Limitation of In-Place Upgrade :

• Operating system architecture switch not possible(from x86 to x64 )
• BIOS to UEFI switch not possible
• Operating system language change not possible
• Changing SKU not possible
• Third-party disk encryption not supported. must un-encrypt before upgrade. Bit locker is supported. 
• Dual-boot or multi-boot systems not supported
• Cannot use a custom image of Windows 10 for In-Place Upgrade scenario. You must use the install.wim image provide in the Windows 10 media
• Ensure all LOB web apps works with IE 11 before OS upgrade