It's A Conspiracy!
Everyone put on your tin foil hats, as I'm about to lay out for you the reason that Tony is still alive.
First off, as explained below, Tony is not scheduled to act in any upcoming films or television shows—so he can't possibly be dead.
Second, why was Tony so quick to want to kill Henderson? And what exactly was he planning to inject the guy with? Maybe he had no intention of killing Henderson, but was trying to help him! He wanted to inject Henderson with the same stuff that Jack took to fake his death last season, to help him escape.
Henderson woke up, didn't know that Tony was just trying to help, and injected Tony instead.
So why didn't Henderson know Tony was trying to help? Because Tony did what every other good mole in CTU history has done—he made everyone think the mole was someone else (i.e. Penis-nose (a.k.a. S4GF)).
But this is where the plot thickens.
Why would Tony try to help Henderson? Because Tony was recruited by Palmer.
Remember Henderson was not working with the terrorists, he was working with the neocons to set-up the terrorists. So was Palmer (which is how he knew about the whole thing and why he wanted to alert President Weasel). The terrorists found out he was a threat, and they were going to take him out—but he found out in time and faked his own death. He didn't have time to warn the others, however, so they managed to take out Michelle (and tried to get Tony) because they were in on it too—not just because it would help frame Jack like they claimed.
So Tony knows that he and Henderson are on the same side, and was trying to save him.
Wayne Palmer is trying to get to the President to tell him that his brother is still alive.
A living Tony is being wheeled into the morgue, but will hopefully come to at some point.
And so, Tony remains without a full X on the banner for this page, at least for another couple of hours.