Data from Average Web Page Size Triples Since 2008 extrapolated to the years 2014 and 2015 via exponential fitting.
Added 26-Mar-2017: Also see Most of the web really sucks if you have a slow connection by Dan Luu. In a more funny form see The Website Obesity Crisis by Maciej Cegłowski.
Using data from websiteoptimization.com I graphed the development of web page sizes over the years. I also included the exponential fit:
As you can see, the 1/2 MB mark was cracked in 2009 and the 1 MB mark was cracked in 2012. Despite the seemingly random fluctuations, an exponential trend is clearly visible. The power 0.3 indicates that the web page sizes doubles about every 2.3 years. Assuming this exponential trend continues we will have these average sizes in the coming years:
2013 – ca. 1600 kb
2014 – ca. 2100 kb
2015 – ca. 2900 kb
So the 2 MB will probably be cracked in 2014 and in 2015 we will already be close to the 3 MB mark. Of course the trend is bound to flat out, but at this point there’s no telling when it will happen.