From Martin Dugard's blog:
"Armstrong also stated that he is an athlete, and will still compete to keep himself fit. He specifically mentioned doing a few running and biking events in his hometown. Then he joked about maybe doing an Ironman in a couple years. He quickly brushed that one aside, but I thought it interesting that he’d been thinking about it."
I've heard Lance mention the word "triathlon" more than once in the last couple of weeks. Everyone knows about his start in triathlon. I'd be willing to bet that he's got an Ironman in the back of his mind for some time in the next year or two.