OK, just for grins...

1. Yes as an OS. No as a choice for people buying a PC or laptop with a pre-installed OS.

2. Now as an OS. Long, long time as a choice as above.

3. Far, far away the biggest problem in moving away from Windblows: business software and Internet Explorer for business use. No other reasons come close. Business will not get rid of Win or IE and most people will use what they use at work. It's familiar and easy to do so.

4. Who knows? No winner most likely.