1) It already has happened. With each new iteration or rehash it makes me more and more go out of my way to see indie films or lesser known releases and broaden my horizons, so to be honest, it's a great thing they do these giant movies, children and casual movie goers enjoy themselves and I get to find out more about my tastes in movies and the opportunity to find new favorites.
2) As always, movie adaptations 99 times out of 100 are at the very best, lackluster, boring and have no positive impact on fans of the video game itself. Hitman, Hitman again, Tomb Raider, BloodRayne etc. The issue is, most video game adaptations are poorly executed, badly researched, money grabs which is a true shame as there are so many untapped opportunities with wonderful worlds to explore instead of the usual, over hyped 'Marvel, DC, Disney' pandering to safe success. When done right, they could be brilliant, but I have never, ever seen one done to a standard I would consider acceptable. I hope this changes, I have very little hope with Assassin's Creed, I am nearly positive it will be 2016's version of Jolie's Tomb Raider, sitting at a 5.7 or 5.8 on iMDb, worth one watch then forgotten about but Warcraft seems to have a team that has used careful consideration behind every decision, from cinematic style, story decisions, CGI and actor choices which leaves me cautiously hopeful.
3) I believe that Rogue One has the opportunity to be what The Force Awakens should have been, but will be a success on its own merits, story line and direction.
2016 looks to be an exciting year in movies if the early releases are anything to go by and some very big films being released. A new era of directors with different taste and technique are making their names known and I shall keep on developing my film tastes all the while.