For several years now, the future of Wikistats has been declared uncertain, see for instance «future of dump based Wikistats scripts is uncertain (HADOOP will likely take over)» on bugzilla:46198#c2. When can we hope to have some decision/indication of what the WMF is going to do? There are only some scattered and semi-abandoned notes on Meta currently (I'll add links to this page).
Whatever you decide, please remember to give additional points to whatever is more likely to be adopted and co-developed by the sysadmins and users of other thousands of wikis. Wikistats was used by some other large farms and m:StatMediaWiki has seen some usage in the wild; I'm rather certain that almost nobody is going to set up hadoop clusters, on the other hand.