Well, that soldier was played by actor Sam Witwer, known for his role on Being Human on the SyFy Channel today. And according to Witwer, The Walking Dead creator Frank Darabont pitched him an idea of a web-based prequel show around his character. It would have included weekly uploaded episodes featuring the story of this soldier and everything that happened in Atlanta leading up to him being alone in that tank. And it would have ended with Rick crawling in through the floor.
Unfortunately, when Darabont left the show, the plans for this web-series also went kaput. Witwer, was completely prepared to film around his schedule at Being Human too. And we can only guess how many other great web-series prequels and side stories Darabont might have brought to us via the internet. However we are not completely without extras on the web. AMC does have some web-i-sodes featuring The Walking Dead characters, along with other documentaries, interviews, and trailers at: http://www.amctv.com/shows/the-walking-dead/video. But this story about the soldier in the tank would have been pretty cool.