But then of course there's 10.7 Lion, Steve Jobs' Operation Market Garden, where scrolling was screwed and Rosetta was removed and Java was jettisoned (wait, that's a good thing) and scrollbars were iOSified and Save As was deprecated and you can't tell if an application has quit or not. And like 10.6 left behind an entire generation of Macs -- every Power Mac ever made -- 10.7 left behind every 32-bit Intel Mac, and 10.8 won't even run on those 64-bit Intel Macs that can't boot a 64-bit kernel, including my 2007 Core 2 Duo Mac mini which I use for taxes and Android stuff. 10.8 does smoothe out some of the rough edges of 10.7 but doubles down on them in other respects, and why bother
downupgrading to 10.7 if I can't upgrade to 10.8 as quickly as possible thereafter? I could boot 10.7 on my mini, but then I lose all the features I need from 10.6, I can't upgrade to 10.8, and I have no apps that demand either one. So 10.6 stays.
In that context, then, I suppose it's not surprising that Mozilla (and probably Chrome as well) has a problem: 43% of their users are on 10.6, an OS that Apple is supporting pretty much in name only right now and will almost certainly cease to after 10.9 emerges (expect word on that from the incredibly oversubscribed WWDC). And why is this? Well, look at the other two numbers: while 10.8 is growing, 10.7 is at 30% and dropping. I can't be the only one who made the calculation that it's better to stay on 10.6 if you can't go to 10.8, and there are still lots of 10.6-only machines in use that really aren't that old. Since Apple isn't maintaining Safari anymore for 10.6, it's alternative browsers ahoy.
Unlike previously premature attempts to kill off platform support on Mozilla's part (ahem), there's a big operations problem brewing here. Apple is obsoleting hardware faster and faster, and Mozilla can't buy more 10.6 or 10.7-capable systems because Apple won't make them. (Used hardware is not generally acceptable for the types of testing they need to do; their Mac mini build farms work very hard.) They might be able to build on a later version of OS X (but not for much longer?), but they wouldn't be able to test how well it works on earlier ones. So they're going to repurpose the 10.7 test systems for 10.6, since it continues to be the majority of Firefox's OS X user base, and make 10.6 and 10.8 the major test platforms until Apple finally has a developer beta of 10.9.
All this is good news for us, of course. On the dark day when Mozilla makes 10.7 the supported minimum, all supported Macs will run a 64-bit build, have hardware acceleration, and use the new UI and related libraries -- none of which is true for us (we still use some Carbon code, limiting us to 32-bit even on G5, we don't have hardware acceleration, and our scrollbars are actually visible and scroll in the correct direction). At minimum we would have so many changes to pull forward that we would almost certainly have to split off separate widget and theme subsystems, and merging work would increase significantly if we could get it to function at all. But with almost half their users on 10.6, even considering that the number is slowly dropping, I'm now not anticipating this will occur until at least the next ESR and the chances of a working TenFourFox 31 have just increased big time.