It seems like we're meant to assume the Akatosh statue serves the same purpose as the Dragonfires. I'm not sure if that makes it the stone, or just a replacement for the effect the stone had on the barrier between Oblivion and the Mundus.
We've seen nothing before to imply that stones are indestructible. The one in Red Tower was removed. (NOT destroyed. If the Heart of Lorkhan were destroyed there'd be no world anymore.) So Red Tower is basically "switched off" right now. The one from White Gold was removed with the death of Uriel.
With these precedents for rendering towers useless, one can only assume destroying the Akatosh statue would be possible. I'm sure the thing is more heavily guarded than almost any other location on Nirn for that very reason, however. The Battlemages, the Elder Council and Emperor Titus Mede probably are more aware of this than anyone else.
Perhaps THAT's the reason the Synod was commissioned - a holy order to root out Dagon worshipers and other evil cultists plotting to remove Stones and weaken the barrier?
We've heard later that the Mane is assassinated, and some people speculate that he acts as a stone in a similar way Uriel does, but that's speculation at this point. Umbriel was able to enter Mundus, although it's still technically not fully in the world. Perhaps the death of the Mane weakened the barriers, but to a lesser degree than before?
Hmm, so if the Heart wasn't destroyed, where is it now?
Also, is there anywhere I can take a quick look at the summary of the events of the fourth era? Without purchasing the book of course, though I fully intend to, I just wanted something to look at in the meantime. It's rather important for a story I am working on. Thanks
EDIT: Nevermind, did a quick wiki search and found most of what I was looking for. Thanks anyways