The idea is that Chaos Legion production points is the "base line."
Rebellion is currently half of Chaos Legion as well as Conclave Arcana.

The team announced in the Town Hall that when a set rotates out of Modern, the production points will increase and move up to match Chaos Legion.

So as of right now, if nothing changes...
When Rebellion rotates out of Modern, the production points will equal Chaos Legion.
When Conclave Arcana rotates out of modern, the production points will equal Chaos Legion.

It's basically saying "that's the lowest amount of production points for land that a wild card will have.