Will we be able to LE to manage SSL certs for things like IBM Domino? Barracuda devices, etc??
Anything where you can complete one of the challenges and directly or indirectly feed PEM encoded X509 certificates into.
Anything that accepts a certificate will work, really. Right now, you do need to use webroot authentication (either automated or manual) to validate the request, but even that only requires that you can serve a file over a web service of some kind for the validation.
Given you can convert the data into basically any format from PKCS12 (useful for IIS or Java) to JKS (Java) to even that weird XML format .NET uses, I can’t think of a situation where it wouldn’t work as long as the service uses certificates.