If you look at the land use strategy document, it highlights several locations as potential sites for 'catalysts for regeneration', which for QPR means the stadium - up near Willesden Junction, at Hythe Road a bit north of the Scrubs, near North Acton station and way over in the middle of Park Royal. I may be wrong but I don't think any of these are on Car Giant's land*
Buried deep in one of the many PDFs from the GLA is this statement:
5.15 During 2014 and early 2015 Queens Park Rangers Football Club has held pre-application discussions with the local planning authorities and the Greater London Authority on the potential for providing a new football stadium at Old Oak. The development of a new Football Stadium and appropriate associated development within the OPDC area could be supported, subject to it meeting appropriate planning requirements and securing land agreements, as it could provide an early catalyst for regeneration and a vibrant focal point for the development.
* on closer inspection, the Willesden Junction and Hythe Road sites may need at least some Car Giant land, they are also the closest sites to Shepherd's Bush and due to be developed before HS2 is opened (2026....ha ha ha). I can't find anywhere where it says when decisions will be made, but there seems to be an assumption that work starts next year. The whole thing will take 35 years to develop.