Never is a long time. I see what you are saying, though. Some parts of M-theory may well border on the philosophical. I’m a big fan of Sci fi also - few of my favorite authors are Larry Niven and Orson Scott Card (who, interestingly enough, is very religious). And it’s science-based fiction - just because the word Fiction is there doesn’t mean that some real science and very clever theories aren’t presented. Did you ever read James Blish’s “A Case of Conscience”? I’m pretty sure you would enjoy that one - I did.
http://en.wikipedia.org/wiki/A_Case_of_Conscience
Don’t be so doubtful of what humanity is capable of - look at what our imaginations have come up with (sci-fi is but one example) I can envision a day when we can harness the entire energy output of a sun (Dyson Sphere), or perhaps pull energies directly from higher dimensionalities. Maybe then we can test M-theory
I’ve had the same argument with my physicist friend regarding human capabilities. He helped build the world’s fastest computer (at that time) to make a calculation for his physics. I have to concede that the greater practical knowledge of our limits is his though; he’s actually run up against the limits of testability while I just have a hazy idea that everything is possible and then don’t have to actually make it happen.