I suppose there might still be a distinction, though, along these lines: SBH is, for many people, the skirmish game of choice. But is any version of D&D the go-to game for many people for pure skirmish wargaming?
Well, no, but it might have happened. The 2000-ish (was it 2001?) version of Chainmail from WotC was explicitly a minis skirmish game that used a simplified variant of the brand-new 3.0 rules, and it was launched to enormous critical acclaim and had a very good reception locally. Won best new minis rules of the year at GenCon (or was it Origins?) on release. And despite that, WotC cancelled the game and its metal minis line and replaced it with an even more streamlined rules set and the plastic prepaints of the D&D Miniatures line. And those sold in phenomenal numbers, and the rules were popular for years to come. Certainly reached a far wider audience than SBH ever has, and that wasn't entirely on the strength of the license.
I've heard very good things about 13th Age. I gather it's being used - officially - with the Glorantha setting.
Yes, there's a licensed Glorantha version, although I haven't had a chance to try it yet. From what I've heard (and what little I've seen in previews) it's doing a way better job of staying true to Chaosium's version than any of the other licensees have (looking at you, Mongoose). The Icon & relationship rules certainly fit the setting well, at least for heroquest level play.
You can read the mechanical parts of the core 13th Age rules here:
http://www.13thagesrd.com/Regrettably that misses out on the setting and the designer notes and commentary, which is a big chunk of the coolness of the game as a whole. Still gives you some of the good stuff, and a fair idea of how the crunch of the game works. It is very much akin to an evolved D&D 4E, which may be a negative for many folks, but IMO it trims out the worst elements, touches up the good stuff, and adds some really clever innovations. Worth a look for use in D&D style dungeoncrawling with a bit more heroic gameplay (ie low level characters aren't super fragile).