This isn't true. In Spring 2016, the City of a Toronto approved plans to move forward with the entire Relief Line, from Dundas West to Sheppard-Don Mills.
Toronto City Planning is currently finalizing plans for the Relief Line Short, from Downtown to Danforth. The TPAP and project design for that project will be initalized in early 2017 and concluded later that year, bringing that phase of the project to shovel-ready status. Immediately thereafter (should be around late 2017/early 2018), Toronto City has said they will begin planning for the extension from Danforth to Sheppard. This includes the TPAP and project design, which will bring that extension to shovel-ready status. I haven't seen any timeline for completion of that phase, but based on prior projects, I'd expect the Relief Line extension to Sheppard to be shovel ready in 2020/20201. Immediately after planning for the extension to Sheppard is complete, Toronto City Planning will commence planning work on the western extension to Dundas West Station.
We're really close to changing gears on the Relief Line. In a years time we should be seeing a lot of work on the extension to Sheppard. Alignments, station locations, service planning and all that good stuff UT gets excited about. Exciting times.