Milestone goals are pretty meh. I mean, they're not bad, but they're basically say "we'll make more game with more money!". Well duhhh. The milestones still rely on the "Help Obsidian make a video game" hook, which I don't think will work in the long run.
People like myself who already want what they're offering will, mostly likely, have donated by now, or planned to donate sometime in the near future. Sustaining funds requires convincing people who on the fence, or disinterested, that this game will be worth it. Some insight into the world they're planning to create, story hook, concept art, themes we can look forward to exploring, and such would go a long way.