Suppose you're a large RPG company with a penchant for "re-imagining" beloved games and campaign settings. Suppose, too, that you happen to hold the rights to the campaign settings of not one but both the creators of the first and best-selling roleplaying game of all time. How do you best leverage your rights to those settings in a way that simultaneously doesn't deviate from your commitment to make things "fresh" and does justice to the 30+ years of history associated with those settings? Well, if the decision were mine to make, this is what I'd do: become more Roman than the Romans.
Let me explain what I mean. Both Blackmoor and Greyhawk have at least part of their origins in the Domesday Book map of the Castle & Crusade Society of the International Federation of Wargamers. Issue #13 of that periodical included an early version of Blackmoor, well before OD&D was ever published. Theoretically, both the Greyhawk and Blackmoor campaigns existed in the same "universe" established by the C&C Society map. Echoes of this reality can be seen in the existence of a northern realm of Blackmoor within the World of Greyhawk and of a "Great Kingdom" in each -- a formerly good and noble realm that fell to evil and despotism and against which several nations rebelled. Likewise, there's also a Duchy of Ten(h) in each setting, whose name, legend has it, derives from its existence in section 10 of the C&C map, which was parceled into "land grants" to be given to C&C members to develop on their own.
Of course, the histories of Blackmoor and Greyhawk are more complex than that -- convoluted even -- but the point remains: they share a common origin. So, if I were going to "re-invent" these settings in a way that might grab the attention of both contemporary gamers without any knowledge of the hobby's past and old timers for whom honoring the past is important, I'd go back to square one. I'd find some way to recreate the old C&C map, place both Blackmoor and Greyhawk on it, and do my damnedest to reconcile them or at least integrate elements of both, along with new material that draws inspiration from the originals.
The result would, of course, be something new and even, to a certain extent, ahistorical but its newness and ahistoricity would at least derive from a careful examination of the origins of both of these seminal campaign settings. I'd probably go ahead and get in touch with as many people who were involved in these campaigns in their formative stages and let them tell me stories about those early days. I'd mine every bit of information I could get my hands on and use it as a springboard for creating a hybrid Blackmoor/Greyhawk that would satisfy the twin demands for "freshness" and respect for the past. Grognards would still grumble, of course -- that's what we do -- but this time the grumbling would be about how I'd failed to respect later publications, not that I'd failed to respect the prehistory of these settings, the crucibles out of which our entire hobby was born.
So that's the cockamamie plan I'd undertake if I held the rights to both Blackmoor and Greyhawk and didn't just want to rehash what we've seen over the last 30 years. I'd go back to the original sources of all this stuff and make the case that I was being super-true to the past by taking my cues from stuff that's largely been forgotten, even among grognards. It might not work, but at least it'd be genuinely different.