if you are referring to the XceedComponents.exe packages, you won't be able to install multiple version side by side. If you are referring to the Xceed_Ultimate_Suite_vX.Y.exe package, you will be able to install multiple version at the same time.
Please note that the ActiveX components, either installed by the XceedComponents.exe or by the Xceed_Ultimate_Suite_vX.Y.exe, won't install side by side. As explain before, unless making a completely new component, the way ActiveX are registered do not allow multiple instances to be registered at the same time.
Hope this help!
Xceed Software Inc.