In 2008, Wizards of the Coast made a huge change to the Extended format rotation policy: Instead of some "rotates every 3 years" policy, Extended would simply carry the last 7 years' worth of Magic blocks and Core Sets.
In 2009, Wizards of the Coast announced that Core Sets would rotate with the block that immediately preceded them.
It's 2010, and Extended's changing again, more on tune with the 2008 announcement.
Starting July 1, 2010: Extended will now only contain the last 4 blocks and their related Core Sets ("related" means "the Core Set that was released after a certain block finished"), rather than the last 7 blocks + their Core Sets.
As of July 1st, then, the following rotate out of Extended for being outside this 4-year limit:
Champions of Kamigawa
Betrayers of Kamigawa
Saviors of Kamigawa
Ravnica: City of Guilds
Normally, Coldsnap wouldn't rotate until Time Spiral block rotated, but Wizards of the Coast wanted it 100% clear that the only sets legal were the last 4 blocks plus their related Core Sets.
That leaves these in Extended:
Shards of Alara
Rise of the Eldrazi
Magic 2011 (after it releases July 16th)
Extended will rotate once a year when a new block starts. So when Scars of Mirrodin becomes legal, the oldest block (here, Time Spiral Block) will rotate out, as well as its related Core Set (in this case, 10th Edition).
In essence, then, the new Extended is like a Super-Standard, keeping sets legal for 4 years instead of just 2.
This new list does have an Extended Format Banned & Restricted List. It's only 2 cards big, and they'll both rotate out when Scars of Mirrodin releases:
Hypergenesis (Time Spiral Rare)
Sword of the Meek (Future Sight Uncommon)
Hypergenesis is seen in a Cascade-style setup. A Hypergenesis player will work to get at least 2-3 good big creatures in hand, then they'll cast Violent Outburst with Hypergenesis being the only card lower than 3 casting cost in the whole deck. Creatures of choice usually involve flying plus having some "enter the battlefield" effect (like Angel of Despair)
Sword of the Meek was used with Thoper Foundry to generate many 1/1 tokens in a turn and then use Time Sieve to gain extra turns or Tezzeret the Seeker to beat face with flying 5/5's (plus the 5/5's that Sword of the Meek + Thopter Foudry will each be).
Both combos would be pretty dominant after this new rotation, thus the decision to ban the cards that will rotate out in a few months rather than the ones that will rotate in a few years.
Wizards of the Coast claims low Extended tournament turnout for the change. The card pool was too large (7 years' worth of sets, at times more under the pre-2008 change), and even though it goes pretty far back Extended still rotates so players would gravitate toward Legacy more than Extended to keep good use of their older cards for a much longer period of time.
This leads to the possibility of more "casual level" Extended tournaments. Before this change, Extended was the realm of Pro Tour Qualifiers, Grand Prix tournaments, and Pro Tours. Now that Extended will be more accessible, FNMs could potentially crop up for Extended now.
AS FOR LEGACY:
Legacy didn't get away in the free and clear. One new banning comes in the form of Mystical Tutor. Mystical Tutor is seen in Sorcery-based decks that must have their key Sorcery card quickly. I guess Legacy Reanimator (featuring Entomb) and Tendrils of Agony-based Storm decks started to become too dominant just because of Mystical Tutor, so it got the axe.
For that one card going away, though, we got two back: Grim Monolith and the ever-complicated Illusionary Mask.
While I don't know the reasons for the Legacy banning and unbannings, there should be an article on the official home page Monday or sometime next week detailing the reason for the changes.
Until next time, enjoy!