Trust me, it will go down and cut-off should go below 450 in the next 6 months. I got my ITA under 481 draw and I declined the invitation for other reasons and I know atleast 3 more people like me who declined it because of not being able to get the documents on time, so not all of 1680 people who got ITA will apply for PR.Which means there will be future draws with lower cut-offs. Lastly, let me tell you, there are not that many people above 481, they might be around 1000-2000, but look at the bigger picture, CIC is targeting 25k immigrants or more. 2-3k people are nothing when compared to 25k. so the cutoff will eventually go down.
Hope for the best!