Looks like my hunch was right.
Scott Rouse, Brand Manager for Dungeons & Dragons at Wizards of the Coast, has made the announcement over at ENWorld:
“There will not be tiers within the OGL.
There will be Wizards official D&D products (which will include licensed D&D products for foreign language translation) and OGL products made by third parties like Paizo, Expeditious Retreat, etc.”
For those who don’t understand the difference, I’ll sum up: The Open Game License (OGL) is the license that allows publishers (and non-publishers, for that matter) the right to use core elements of the rules system that drives Dungeons & Dragons. The d20 System Trademark License was a secondary license which allowed publishers the right to use this symbol:

to indicate compatibility with those rules.
This announcement means that while there will be Open Content in the forthcoming 4th Edition of D&D, allowing publishers to produce 4e-compatible products, there will NOT be a d20 System Trademark License. No official logo to show that your product can be used with D&D.
I’ll be interested to see how this shakes out, since it will now mean that there will be a push for publishers to come up with methods of indicating compatibility (expect a dozen or more competing logo co-ops, with various publishers signing up for each…as well as a few dozen more publishers who go their own way and use their own sole-use logo), and it will require a lot more product-knowledge savvy on the part of retailers and consumers.
It does affect me directly, since it effectively means the end of d20 MasterKit as a line, since the trademarked logo will no longer be usable.
Also: Still no word on when, exactly, we publishers are going to get a look at the rules, so we can start prepping releases.