Gartner is always more optimistic about PCs than reality
They only predicted drops after 2+ years of PC sales drops going against their predictions, so they predicted much smaller drops than what actually happened. Due to a brief blip from XP replacement they seem to be thinking growth is back on the table, but that blip will be past before the year's out and it'll be back to negative growth.
Gartner continues to not understand just how much of the PC business has been based on people who have very modest needs from a PC, which can easily be satisfied by a tablet or smartphone. Same mistake techies make when it is suggested to them - they defend all the things they do that they couldn't do on a tablet, but it isn't about people who work with computers 8 hours a day. It is about ordinary people who use them 8 hours per week or per month.