Status as of 2015-06-24
The Web Tools Platform's 3.7 release is now available, aligning with the Eclipse Mars Simultaneous Release. WTP is featured in the Eclipse IDE for Java EE Developers and also contributes to many of the other Mars packages. You can also download WTP builds manually or install just the features you want by working with the Mars Update Site.
WTP 3.7 was officially released on June 24th, 2015.