tmhg has made some valid points. OS4 versioning and pricing seems quite random and gives no confidence about the future. If I had bought OS4.1 I would expect free upgrades to OS4.1 until OS4.2 is released. Just like Windows service packs or AmigaOS boing bags are free and always have been.
By preannouncing FE weeks/months ahead Hyperion have shot themselves in the foot somewhat, as no one is likely going to buy the existing version of OS4 now for hundreds of dollars and not get any updates.