And no one else has any concrete information.
There's a bunch of concrete information out there. Amazon is pretty generous with information, and compares with other companies.
For one little bit of information, on Amazon, the Pathfinder Roleplaying Game Core Rulebook is #2,133 in book sales and there is no used books being sold under what Amazon would charge. The 4E PHB is #7,504 in sales and gently used books are being sold at 25% off--many of them labeled as remainders. 2E and 3.0 can be had for $6 (including shipping), but 3.5 is $25, $30 (including shipping) if you want one in good condition, and is #5,432 in sales.
Bestsellers in Gaming
#1: 4E Rules Compendium (#416 in sales)
#2: 4E Heroes of the Fallen Lands
#3: 4E Dungeon Tiles Master Set - The Dungeon
#4: Warhammer 40K RPG: Deathwatch Core Rulebook (#1,380 in sales)
#5: Dungeons & Dragons Fantasy Roleplaying Game: An Essential D&D Starter (#1,963 in sales)
#6: Pathfinder Roleplaying Game: Core Rulebook (#2,133 in sales)
#7: Lords of Madness: A D&D Miniatures 6-pc Booster Pack
#8: Pathfinder Roleplaying Game: Advanced Player's Guide (#2,814 in sales)
#9: 4E Essential Dungeon Master's Kit (#2,857)
#10: 4E D&D Gamma World Roleplaying Game (#3,781)
#11: Dark Sun Campaign Setting: A 4th Edition D&D Supplement
#12: Player's Handbook 2: A 4th Edition D&D Core Rulebook
#13: Monster Manual 3: A 4th Edition D&D Core Rulebook
#14: Psionic Power: A 4th Edition D&D Supplement
#15: 4E Essentials Heroes of the Forgotten Kingdoms
#16: 3.5 PHB (#5,432)
#17: 4E Essentials Monster Vault
#18: Rogue Trader: Into the Storm (Warhammer 40,000 Roleplay)
#19: Pathfinder Roleplaying Game: The Pathfinder Bestiary
#20: Player's Handbook 3: A 4th Edition D&D Core Rulebook
#21: 4E PHB (#7,540)
just looking at core books
#24: Dungeons and Dragons Core Rulebook Gift Set, 4th Edition (#9,598)
#29: Legend of the Five Rings 4th Edition RPG (#12,552)
#36: 3.0 PHB (#16,744)
(There are no systems not otherwise noted in the first 36 books.)
So D&D is still the monster of the roleplaying world. The problem is the forms of D&D are not entirely controlled by Hasbro; both Pathfinder and D&D 3.5 have significant followings. I'd say the fact both the Pathfinder core rulebook and the 3.5 PHB outsells the 4.0 PHB at Amazon is a big deal, along with the fact that the 4.0 PHB is starting to get remaindered and is starting to get undercut by used copies.