According to a Google study, the mobile internet pipes are getting faster. Google used their Site Speed reports from Google Analytics and opted-in web publishers to get an idea of the speed of websites around the world. Google has again aggregated that data into the following graph:
As you can see, on the desktop side of things, not much has improved from 2012 to 2013. Speeds are just slightly better, but not by enough to really have much significance. On the mobile side of things, however, the mean time to load has decreased by about two seconds. The median time has decreased by about one.
Google credits most of these speed increases to LTE/4G roll outs as well as increased processing power in mobile devices. Read the full Google report.