Arcane was a type of spell that first debuted in Champions of Kamigawa. It was a closed mechanic that was supposed to represent the “Spirit World” Magic which is different than “Magic” Magic and for the first time gave instants and sorceries sub-types. The down fall is that they can’t be reprinted unless Arcane is reprinted, but that was only a block mechanic. While I said that I wish that Arcane was revisited, it looks like Wizards is taking spells that were Arcane only and now making functional reprints without that subtype.
At the Seattle M11 Prerelease, I was talking with some of the employees of Wizards of the Coast and I brought up the whole “Sixth color is coming to Magic” thread from MTGSalvation. All of the guys started laughing and saying that sometimes people read too much into things. If you don’t know how it started, one person looked at the art for Time Reversal before the card was spoiled and said “Hey, there are six colored planets (one for each color and purple) on this art and MaRo tweeted that a future set will have players the opportunity to draft something they’ve never been able to. That must mean Purple is coming to Magic!” It’s a very fun thread to read about how some people do read too much into things.