Asuran Time Machine
The Molten and Aetherblade dungeons are being added to the fractals later this year, so they will be able to be played for those who missed them.
For the rest, I’d personally prefer a SAB style holodeck to a time machine.
Fractals of the Mists dungeon is time machine -ish.
It would turn out like this: “Dessa has discovered how to relive the past Living World through Fractals of the Mists.”
Edit: Dessa: http://wiki.guildwars2.com/wiki/Dessa
(edited by Exosferatu.2961)