I don't think so.I'd like to put the Death-Blade on the table. (X stands for Death) The Death-Blade is a Keyblade, if we can confirm that and that the Death-Blade was made from Van and Ven's hearts we can say that if a Keyblade is destroyed the heart that created that Keyblade is destroyed with it.
If MX destroyed his Keyblade or was destroyed then his heart would be lost with it and I believe the same rules would apply vise-versa.
If that was the case, then wouldn't Ven be dead, because his frozen keyblade got smashed on his little fall from on top of MX's plateau before the final boss fight. His keyblade just came right back to him. I don't think it's possible to destroy a regular (not keyblade of people's heart/X-Blade) keyblade.
And MX isn't dead, he just lost all his memories and is in some weird situation where he shares a body with Terra. Not dead, though, as you can see from the BbS secret ending. In fact, that movie seems to imply that MX's heart is the more dominant one in Terra's body.