I'm trying Visual Studio 2012. I can open VS2010 solutions with VS2012` which is fine and expected, but what I wonder is if we can open VS2010 solutions without changing them. I want this because we use a source control system and some members of our team still use VS2010, so I don't want my solution file changed.
Unlike previous versions of Visual Studio, I don't think that VS2012 makes any change to VS2010 solution files at all when you open them. That's why there's no prompt.
The simplest thing is just to open the solutions as an experiment - maybe make some change that you'd normally want to make, e.g. adding a new project - and then diff your file to the one in source control. I'd expect it to be fine. When you've finished your experiment, just revert your local changes either way (assuming they're not changes you want to actually keep), and you'll be away.