Canada conducts rounds of invitations every fortnight. High ranking candidates are thereby selected from the pool of immigration aspirants. To get selected, thus, you need to have a highly competent score which is between 400 and 500. If we go by the latest trends of Express Entry CRS draws, those with score range of 420-450 holds a decent chance of getting selected.
In light of announcement which state that Canada is going to welcome 1 million new immigrants by 2020, a drop in CRS cut off can be prayed for.
However, a drop down to 400 is not a possibility.
If your CRS score is less than 400, then you can consider these ways to improve your score.
If your CRS is above 400 but less than the range bracket of probable CRS draws (420-450), then you can look forward to get Notification Of Interest (NOI) from the province of Ontario.