a) support the legacy systems forever. b) don't support them at all.
Option A leads to a Windows-esque environment where support for older platforms actively holds back development and innovation for newer ones. Option B kills everyone's existing apps. Neither of those sounds like a very developer-friendly or even user-friendly option.
Frankly, the fact that they built those at all shows that they're willing to go the extra mile to make sure that their developers have the heads up to upgrade their applications before breaking them entirely.