It very well might be, sadly enough. Mark Henry's career is currently in limbo. Mark Henry was (according to what I've gathered, this isn't a 100% reliable statement) expected to hold the World Heavyweight Championship all the way until WrestleMania 28, where he'd proceed to drop the championship to Sheamus. Mark Henry's reign was cut short unfortunately in December due to a misdiagnosis of the severity of his ankle injury. He was expected to be out for a long period of time, so WWE took the championship off of him.
Shortly after the injury in which had thwarted one of the most credible championship reigns in the last decade fell through; he remained on air whilst healing. Upon his continuation to work, the "minute" injury he'd suffered was exasperated, and subsequently may have cut his career short. Henry's been vocal saying this injury could be the end of his career, and he's awaiting the results post-rehab to see if he'll return. I believe Mark Henry was filling a void that WWE had needed to be filled ever since the unfortunate circumstances behind the release of Umaga, that led to his more so unfortunate passing. That being, a believable upper-card monster heel. Henry brought both legitimate ability, knowledge and experience to the table with a chip on his shoulder. Along with literally being deemed on of the strongest men on this planet, he oozed credibility.
I believe if Mark Henry's injury does not result in the ending of his career, he'll get another crack at the main event. Did you watch his bouts with CM Punk post-WrestleMania? PHENOMENAL matches, and I could see Mark Henry making either a short run as a WWE Champion, or he'll be given the ball to run with the World Championship for a lengthy period of time.
Furthermore, The Great Khali's World Heavyweight Championship reign was merely of circumstance. Mark Henry's run was deliberate and an office decision. The company built Henry up specifically for Randy Orton to put him over, huge. Cleanly, on multiple occasions. As for The Great Khali, I don't honestly know if he'd even still be employed if not for having been the only real heel with any luster in a pseudo-main event capacity upon Edge having torn his pectoral. The Great Khali was an easy choice to make, as he could feasibly pass Kane on by and play games with Batista until subsequently putting him over. Did I enjoy such? Absolutely not. Khali was one of the most boring champions I can recall (other than Alberto Del Rio) though of course, that's merely in hindsight with my personal bias intact.