There are loads of Programming Languages. And many of them have their own .NET implementation. So my doubt is whether all languages can be ported to .NET or is there any requirement that a language need to have in order to be ported to .NET ?
Consider .NET as a highly potent CPU, unless the language relies on a specific machine instruction there's nothing that stops you from implementing it in .NET (or Java or, or , or..).
Of course, some languages have rules about how to handle memory etc that can be hard to archieve transparent to .NET's basic ideas. It will probably be able to do it, but it might violate some basic principles how .NET code should work.