Its not 100% True. Sylveon is SE against Ice. Ice was never mentioned in the leak. Therefore the information is partially fake if not all fake since the names were not included with that post. Since it says specifically all of Fairy's Strengths and Weaknesses and says Sylveon is Fairy typed, and now that we know Sylveon is SE against Ice we can conclude that all rumors on fairy since none have ever said anything about Ice are false.
You must not play as much as you claim to play. Psychic types are plenty strong and have ran on top along side dragon, dark and others. Alakazam/Starmie/Espeon are currently OU. Dragons also aren't as strong as you claim. Outrage is nice, but it isn't the single most important part of a Dragon type's arsenal. Forcing the use of more Steel....which forces the use of Fighting and Ground, in turn forces the use of more Grass and Water which forces the use of more Fire and Electric. If you continue the cycle it would include every type except Normal to counter what's common.
Types were never the big issue, its the specific Pokemon with stats and move sets. You don't need to update types or nerf types. They just need to make more Pokemon with varying stats.
As for adding new types, no it doesn't open the door for more creativity. It causes more congestion because now you have one additional peg to look at when considering what type to put it into. They may not retype any Pokemon with the new type. How would that help? How would that hurt? Would retyping help the individual Pokemon? Would it hurt the individual Pokemon? How would the retyping make sense? A Pokemon that was once weak to a certain type is now resisting or immune to it. Yes that makes a lot of sense when you add in more types.
We don't need new types. We need better Pokemon of existing types.
We don't need to re-balance the type chart as there was nothing wrong with it. Each type was made specifically to do certain things and have been that way for years. Changing it now makes no sense.