Apple recently announced that they will not accept applications submissions for apps that do not support 64 bits architecture. The deadline has been set in February and then pushed back to June. Nonetheless, if you have a Xamarin iOS app, or are thinking of writing one, you will have to support 64 bits.
Xamarin has published a very good video explaining what you need to take care of. Notably, you will need to update all your referenced components and/or 3rd party frameworks to a version that also supports 64 bits.
In order to allow developers to do this work early, I converted MVVM Light to the new Xamarin Unified API with 64 bits support. I will push this to Nuget soon, but I want to give you the opportunity to start working on this as early as possible. In this spirit, I published the new updated DLLs on my public OneDrive. I also ported my “Flowers” sample from Xamarin Evolve to use the new 64 bits DLLs and the Xamarin Unified API.
Note that this is a temporary solution and I would recommend moving back to Nuget when I update the package there (stay tuned to this blog for the announcement).