According to the announcement, land pricing for legacy worlds will be adjusted to match land pricing of non-legacy worlds. This will result in land values on certain worlds being reduced by 2.5 to 5 times their current value over the course of several weeks. Additionally, Square plans to "re-evaluate" the final price of land across all worlds sometime in late January.
Check out the full post to see which worlds have which pricing and how values are about to change.
[Thanks to Zengarzombolt for the tip!]