I'm afraid I would. I consider it wishful thinking they would address such a small minority share of the customer base with a print product.
(Based on the figure of 50% homebrewers, 25% realmsers, and 25% all other official campaign worlds.
If you consider that probably more than half of homebrewers are open to using Realms-specific material like Volo's Guide to Monsters in their home campaigns, it's easy to see why all product to date has been placed in FR: it covers perhaps 50% of the total customer base. That in itself might not say much, but if you consider that the next possible world placement would probably struggle to cover even a tenth of that (5%) of the customer base it all becomes clear.)
More realistically expect Greyhawk or Eberron support to come through Unearthed Arcana articles.
The difference between Realms and the next-best world placement is probably not as big as 50% vs 5%.
For example, probably about the same % of homebrewers would be open to using, say, Greyhawk-specific material as are open to using Realms-specific material, so in that case it might be more like 50% vs 30%. (Which is still not an argument in favor of setting their next AP in Greyhawk vs the Realms

). This argument probably applies to settings like Mystara and Nentir Vale, but may not apply to settings like Eberron and Dark Sun, which might draw a different % of homebrewers.
I, personally, am more interested in the Planescape/Great Wheel setting. Since the Realms is (I think?) using the Great Wheel cosmology now, I figure the odds of them eventually doing a planar AP are pretty good, since they might be able to get most of the Realms audience, whatever is left of the Planescape audience, and whatever % of homebrewers buy the official APs. So that one might be more like 50% vs 50%. (However, what I
actually want is setting books that cover post-Faction War Sigil and develop
all the planes to the same depth that the 9 Hells and the Abyss have been developed, and
that's got about a 0% chance of happening

)
There is, of course, also the issue of self-fulfilling prophecies. Since everything they've released so far has been set in the Realms, it is probably not surprising that when they survey, they find that most groups using an official setting are using the Realms.
It's also possible that this is their unstated goal. In much the same way that they tried to convert as many people as possible from older editions to 5e, they may be trying to grow the Forgotten Realms audience by converting people over from other settings. See for reference that
forbes interview with Nathan Stewart, in which he discusses D&D as a multimedia brand. The existing multimedia franchise is centered mainly around the Forgotten Realms, so it probably makes sense for them to try to get as many tabletop groups as possible to use Realms material in order to grow the market for their novels, the base for a Balder's Gate 3 videogame, etc. This could explain why they're taking things that were originally from other settings and moving them into the Realms.