that seems a little simplistic. It isn't just the runtimes, but also all the tooling that goes with it. There would be a lot of work involved with recompiling all tooling and runtimes to work on ARM, and would probably alienate a large portion of developers currently using Apple products as a result.

This was already done twice in the past, once on transition from Motorola 68000 to PowerPC, and once on transition from PowerPC to Intel. All arrived with updated versions of interpreted language runtimes. We'll have to see what will they do this time.