It seems to me that ST would really benefit from being open-sourced, but I guess it depends on how much cash he's getting out of it, and whether he can afford to give that up.

I stick with ST because the plugin ecosystem is vibrant, it's hackable in a language I'd actually want to write, there's as much time-saving juice as Vim without me having to learn non-standard keyboard commands for the very basics (sorry, I like my arrow keys and Ctrl+x/c/v, and - god help me - my mouse), and it's not a sluggish, half-complete rip off of itself (cough Atom). I know enough Vim to get around a log or config file, but for serious work, Sublime and my brain are partners for life. (Unless Atom improves dramatically, anyway.)

I don't suffer from the slow development cycle, but I'm sure others do, depending on what it is they need.