Personally, I think they should dump support of older machines without hesitation
With new apps and updates to old apps usually requiring the latest OS due to new APIs, you quickly lose the ability to use the latest apps; therefore losing interoperability with others who are able to upgrade.
Newer machines shouldn't have to be crippled or restricted in some way by the legacy machines demanding equal support out there of OS and applications.
They aren't. Especially as all Macs since the last round of cutoffs have the same EFI and mostly same CPUs, the only difference is hardware such as the sound/Firewire/USB chips. The kexts that control these chips are only loaded when the hardware for them exists.
In the situation where I owned a new iMac and the OS decided to support that older machine at the expense of *not* taking advantage of my new technology in some way, I'd be pissed and think I'd overpaid for something.
So you mean when Apple releases a new iMac touting say a HD iSight camera, they don't actually support it in the OS because they are supporting the old non-HD one? Complete rubbish.
Technology advances happen at a much slower pace than previously, they shouldn't be held back further because a bunch of old machines demand equal love.
Even more reason to support the older hardware. The huge leaps of CPU speed we saw in the early to mid 2000s warranted more aggressive hardware cutoffs as the software was using the extra speed in the CPUs. In more recent years, CPU speed hasn't made anywhere near as much progress as it did before, so the software can't bloat as much without causing slowdown on the latest machines.
Machines today last much longer than they ever used to - Microsoft and Windows machines pretty much perished at the 2 year mark in the past, so my 6 year old iMac running the latest OS (and running it fairly well!) is pretty amazing I have to admit (and will be 7 years old when next year's OS comes along), and something I never expected when I purchased it new.
Machines lasting longer should mean the support for them should last longer, too. You said it yourself, the OS runs fine on your 6 year old iMac so why drop support? I have Mountain Lion running on my 2006 Mac Pro, it runs just as well as Lion did, but it's not supported.
Also Mavericks looks like it has some great under-the-hood changes, and some nice new power user features. Really don't like the name, however... Something like Bird species would have been much more appropriate IMO, Mavericks sounds like something from Redmond.
