Yes, if we had this kind of data for several campaigns, then you could compute a (normalized) <% of goal> vs. <time>, and from that estimate the final <% of goal> for this campaign.

The problem with your original calculation, is you're assuming the rate is constant, which it may be, roughly, for day 3 through day 27, however in these campaigns there's always an uptick right before the deadline. Really, it's that uptick that you want to estimate, based on previous campaigns.

I don't think kickstarter or indigogo release this kind of data though, unfortunately.