Some explanation of LEGO's financial performance in 2017 from the BBC News site.
It was already known that the company had had disappointing sales in North America, but the article also points out over-production issues. There is a connection between poor sales and over-production of course, but some of the excess stock may be in addition to lower-than-expected sales.
If LEGO over-reacts in the opposite direction, i.e. cuts production too drastically in 2018, we could see stock shortages and sets being retired sooner than we have been used to.
Here is LEGO's press release.