All climbers have turned back from trying to summit K2 today it has been confirmed. There must have been a number of reasons for this. Chief among them would have been the time. At past three in the afternoon it would have been a late summit. Going for the summit would have risked a bivouac above 8500m during the night. This would have been dangerous. The deep snow was also slowing them down.
For a picture of the Bottleneck and the overhanging ice seracs Gerlinde Kaltenbrunner has posted a picture of herself on the shoulder of K2.