There is a VERY good reason for why XF received just one non-security update from Feb 2012-Feb 2013. I'm not ashamed or afraid to talk about this chapter in XenForo's history and I don't think it diminishes in any way from the progress that has been made since. XenForo development has been rolling along at a great pace for the last 3 years. No rose-colored glasses required.
Originally, XenForo 1.4.x was going to be last of the 1.x line while work on XenForo 2.0 continued. However it was felt that another features release would be beneficial, so XenForo 1.5.x has just been released. My understanding is, development will now continue in earnest on 2.0. Of course 1.5 will still get fixes and updates, but most attention is now on 2.0. Looking very much forward to seeing what the 2.0 architecture means for addon developers!