A player has his era based on his era at that time, and maybe in the future there will be a great new player emerging and being considered the best player of all time, even though he is in a different era.
Yes but technology will mostly assist with accuracy and fairness. Now that we have made this much progress from the least accuracy and fairness to very high accuracy and fairness, I don't expect much to change on that front. It could be improved by the millimeter for example, when the question arises whether the ball crossed the goal line or whether it should be a corner or throw in (I guess those will also be included in the future). Any improvements there would only have minor impact on future outcomes of the game. The hand of god would of course never have counted and it shouldn't because it is ridiculous. We want players to play at their maximum and that is why we need technological assistance to reduce human error.
I think more will happen with the players themselves. Longevity, physical advancement, both of which can lead to longer careers and hence to maybe new records as they have more games to play and can score more goals. I think it will be more changes on that end.