I will agree with Monster Ride Op... All of the steel coasters, except for maybe Corkscrew, should still be standing, but, they will probably be showing great signs of aging by then, and will all have very short waiting lines due to more technological rides. Park guests may even consider the steel coasters of today very boring. The wood framed coasters however, will probably all be gone. Look at Blue Streak and CCMR, they are already almost fourty years old, and CCMR is already today showing great signs of aging. A wood coaster can be repaired only until it is unpractical from an economic standpoint.