Synthesizing, much of what is said seem like myths, uninformed points of view, fanboy talk or biased propaganda.
This is largely true, though your bullet points are largely correct.
what do you consider to be the future of C# and Java?
Java has been effectively abandoned, and is largely crippled by its lack of good generic and functional programming support.
C# is starting to show its age, where it's difficult to improve upon it more.
I suspect that both will remain the top two most used general purpose programming languages in 3-4 years, though their relative popularity will decrease; Java's faster than C#.
What is real about C# portability?
C# can be ported and it has gotten a lot better due to mobile platform motivations, but the cutting edge and best support will for the foreseeable future be on windows. That said, beginners care about portability WAY more than they should.
As for the other questions, they're vague or outside of what I can speak to. C# is fast enough, and generally, so is Java. Java has worse support for games in general, and I expect that trend to continue.