So I think it is fair to say that War of the Spark is shaping up to have at least the potential to affect vintage in a way very few sets have in the past. There are a number of cards that, while still untested, have huge potential to shake up the fundamentals of the format, including:
Ashiok, Dream Render
Karn, the Great Creator
Jace, Wielder of Mysteries
Teferi, Time Raveler
Dovin, Hand of Control
Saheeli, Sublime Artificer
Some of these cards have very profound effects that attack core ways the format functions, including completely turning off counter magic, Stoping tutoring, etc. Some of these effects are not new, but in many cases being on a walker that can be windmilled out and has other utility has made them far more viable than they would have been otherwise.
Which leads me to the question, how much is too much? Magic is a living game and every release has the potential to change the game, but how much is too much at once? I'm trying to imagine what the format looks like with people having to pair back fetch land use or not rely on counterspells and it truly looks very different.