Redundant thread is redundant. These questions have been asked multiple times in multiple threads.
The answer to all 5 questions is we won't know until they've implemented it. People can guess, sure, but nobody can answer your questions with certainty.
Will sky be soloable/duoable? I don't know, it depends on whether or not they plan to adjust to monsters with our level increase.
Will we get new inventory space? I think everyone will agree that we'd like more inventory space, but will we get it? We won't know until they update it.
Same for your other questions, we're not going to know till it hits. Not sure you expected with those questions, since nobody here can answer them
Edit: Now if you wanted opinions on what people think should happen, not what se will do, then the questions would look like "Should we get more inventory space" "Do you think SE will increase the levels of existing monsters or do you think they'll become soloable. Why or why not?" ect, but with the questions you have, not going to get anything