Quote from Gwar_The_TrolleOverextended is too much like Legacy lite, simple reason why WotC will never support it.
On the surface, this is a risk that Overextended runs. After all, with a larger card pool, it seems reasonable that the format would turn out more like Legacy. Indeed it is overwhelmingly logical that if Standard is the least like Legacy, Extended is more like Legacy, and Modern is even more like Legacy, then Overextended would be the most like Legacy (at least if adding sets is the way that a format approaches Legacy).
But in practice, this is completely untrue. Overextended tournaments are full of decks that never appear in Legacy events, with these unique Overextended archetypes consistently posting high finishes at the tables (take the word "unique" with a grain of salt, because a lot of these decks are admittedly imported from either Extended or old Standard tournaments). Here are some decks that have been going 4-0 in recent MTGO tournaments, alongside some Top 8 finishers from past MTGO events. Take a look at the tournament diversity (Source: http://mtgoverextended.com/category/tno/). Yes, there are some decks here that are similar to Legacy ones (Zoo, Dredge, Merfolk, etc.) But these decks are EXACTLY THE SAME as their Modern equivalents. So if you are worried about a deck being too similar to a Legacy version, then you need to think about that in the context of Modern as well.
Zoo (Same as the Modern version)
UR Pyromancer's Ascension
Burn (Same as the Modern version)
UW Stoneforge (Same as the Modern version)
BW Midrange (extremely different from the Legacy version)
The list goes on. I urge everyone to remember two facts about these lists:
1) The vast majority of these archetypes do NOT exist in Legacy. They are totally unique to a new eternal format (even if they were invented in an older extended/standard). Decks are absolutely lost from Overextended in Legacy.
2) Of the decks that are similar to Legacy ones (Zoo, Dredge, Stoneforge, etc.), these are decks which would ALSO exist in Modern! In fact, they would exist in Modern without losing anything from their Overextended version! So if you are worried about Overextended looking like Legacy Lite, then also worry about it for Modern as well.
Force of Will, Wasteland, Lion's Eye Diamond, Swords to Plowshares, Natural Order, etc. These are Legacy Staples that seriously define the metagame. Without them, the metagame has a huge shift. Overextended represents that change, and it is not under any circumstances a Legacy Lite ripoff. The decklists from tournaments prove this.