The LEGO Jurassic World sets are very popular and many sets are now on backorder at LEGO Shop at Home (US | Canada | UK). With the success of the Jurassic World movie, its not a surprise that the sets are able to sell quickly.
Interestingly, LEGO 75920 Raptor Escape has been listed as sold out with no backorder date listed for North America (available in UK though). LEGO is very unpredictable with their sold out status. At times, they may go back to backorder or availability status. However, in some cases, the set would eventually be removed from production. Note that 75920 Raptor Escape is a Wal-Mart (USA/Canada) and Tesco (UK) exclusive.