You may get by with a decompiler as laid out in http://llvm.org/devmtg/2013-04/bougacha-slides.pdf

And since you'll certainly not be the only one with that problem, Apple making it mandatory for iOS would probably spur development in that area.

I am not so confident : they now require that you ship a 64 bits version of your apps, which can be also be a problem if you use 32 bits only proprietary libraries.

There's a good reason for that requirement. Loading 32bit apps on a 64but device requires loading all the 32bit version of shared libs, massively increasing the memory footprint.