Predictions of future PC sales
Based on the vast overestimates of the PC market from Gartner and IDC over the past five years (they predicted solid growth and totally missed the ~30% decline from the market peak) you should subtract at least 5% from their future estimates. So if they think the market will shrink by 0.5% annually over the next five years, substitute a 5.5% annual decline and you'll probably be closer to the truth.
PCs sold with Vista or later are perfectly adequate for today for 95% of PC users. If they want more speed, a SSD and more RAM will make it work better than most new ones you'd buy today (many of which are still sold with hard drives, or useless 'hybrid' drives) The main driver for new PC sales today are people who don't know it is possible to upgrade their PC and don't realize they could pay someone to do it for less, and corporates who are depreciating and replacing them on a set schedule.
A lot of people who only got a PC for email and web access have no need of one now, they do those things on their phone now.