MacVidCards is correct! Today it may be Handoff/Continuity support, and next time it may that you have to have the latest iPhone to sync calender and contacts... No wait, they already did that! Apple has been doing this since the early days of iCloud.
I think it is scary when Apple uses their market dominance to push users into buying the latest and greatest - that's called "tying" and is illegal under Antitrust laws
I highly doubt that this would become a trend. Apple's strength is it's backwards comparability. Even though there are shortfalls with them like this, there's no big move in this direction and never will be.