Well, considering that the only difference in the early versions of Delphi and C Builder was the tokenizer you could easily switch between languages from Delphi 2 to Delphi 7. When they performed the full migration to .NET (remember D7 could build .NET compatible applications but was not a .NET compiler in any sense of the word) in Delphi8+ this "feature" was lost within the actual compiler itself.

The thing is, you don't need Delphi to do this if your using the .NET platform. You can simply bind the C/C++, C#, VB.NET, etc... extensions directly within your code. Just include the namespace and go. Of course, the problem in most cases is that the older C/C++ code won't build under the new .NET platform without a few minor tweaks.