Six Flags this week completed an $8 billion merger with rival Cedar Fair to create the largest amusement park operator in the United States. Together, they operate 42 amusement and water parks across 17 states.The success of the deal will determine the future of these amusement parks, and diehard rollercoaster fans are watching carefully. Some are optimistic that the condition of Six Flags’ parks will improve. Others worry it will become more expensive to get into their favorite parks.Many amusement park fans are passionate about the parks’ design and history and notice the smallest of changes. For now, each park in the new company will keep its old branding and name. But fans fear the parks could lose their nostalgic elements and become a sea of corporate sameness.“There’s apprehension,” said Bill Kneass, who has been a Six Flags season passholder on and off (but mostly on) for 30 years, twisting …