There were proposals from a local football club a few years ago to sell their existing ground and build one on the freight liner depot. There was consideration given to having the speedway as tenants.
All came to nothing though
https://www.expressandstar.com/news/2012/05/17/dudley-heathens-stadium-plan-gathers-momentum/
I'd be very surprised if that was the case however it's certainly possible that Thurrock Council could insist on motor sport provision. I'd think though that if it went to appeal I couldn't see the government planning inspector upholding that.