Network Rail has published their Future Strategy report and it doesn't make good reading for Mablethorpe and Theddlethorpe.
They have no plans to restore the passenger rail link to the search area as they say it would not generate sufficient passenger numbers to justify it. They go on to discuss the proposed rail link to the GDF site with their preferred route running through to Boston via Skegness. Despite their statement that it would not cost a lot more to build the line to passenger standards, they make no provision for stations anywhere along the line.
Even if the line were constructed to passenger standards they would still have to find an operator to take it on. Considering the reason Network Rail put forward for not building the line it must also be doubtful that an operator would take it on.
Lincolnshire section of the report can be downloaded here.