The timing of this is pretty interesting. Apple's been able to make such a tool for years, but the trend has clearly been iOS -> Android for a while. Now that they're finally offering devices in sizes people want (literally 80% of the new iPhones I see are the 6+), people who wanted the bigger devices but went to Android, are finally seeing a reason to switch back. Furthermore, iOS is finally in good shape compared to Android w/r to features like notifications, multitasking, etc. making the idea of migration parity simpler.

I don't think this will have a huge impact in conversions, I think the path Apple is on is already doing that, but it's not a terrible idea.