I never found the theme itself useful, but it was great for picking through and finding useful bits. I was always wondering how long it would take to reach this point. I don't really think it is feasible to provide backwards compatibility whilst adding modern best practices for existing users (without requiring significant code upgrades or significantly breaking existing sites). Some themes, such as Genesis, simply add a toggle to upgrade to backwards compatibility breaking features (Genesis HTML5 mode), but that's not really any different to just creating a whole new theme. I think discontinuing is the best option here. It's probably time for users to upgrade to a newer theme with all the new bells and whilstles anyway.

Big props to Ian and co. for keeping it maintained for so long anyway. Most developers would have dropped support a LONG time before this.