No, we know one other thing about it: it will be produced by WotC, and is therefore likely to conform to their standards, because they probably wouldn't publish it if it didn't. That, IMHO, is sufficient basis for presuming it will be noticably inferior to M&MM. D&D3E/D&D3.5E is inferior to Everquest D20 for hack-n-slash/dungeon-crawl/power-up play. D&D3E/D&D3.5E is soundly trumped by Arcana Unearthed/Evolved for capturing the essence of "D&D". Iron Heroes is much better than D&D3[.5]E for making tactical combat both playable and fun. Spycraft is better than D20 Modern for everything but "modern D&D"--and Spycraft+[something fantasy] is gonna be better than either. Spycraft 2.0 is better than that. That other arctic book (whose name i'm blanking on) was more interesting than Frostburn. T20 is better than D20 Future. There are several D&D monster books far better than anything WotC has produced. Forgotten Realms is perhaps the least-interesting fantasy setting published for D20 System. Similarly, when i start looking at significant sub-systems (such as Spycraft's action dice vs. D20M's action points), the WotC version is usually inferior. Quite seriously, the only cases where WotC has done as good of a job or better than the competition on a topic are when it was a completely outside job and it just got published by WotC for branding reasons--like CoC D20. [obviously all in my opinion, but i *have* looked at all of these, and am prepared to back these claims up with specific criteria/examples.]
So, based on WotC's track record of the last 8 years or so [i continued to find the occasional D&D product i wanted right up 'til TSR folded--despite giving up on playing D&D in '93; i haven't seen a WotC product worth buying since then, even while playing D&D with D20 System for the last 4 years], i consider it a safe pronouncement that D20 Superheroes won't be as good as M&MM.