I just heard this afternoon there are still some new FC-100DL tube assemblies at dealers scattered across the country so you can still buy these new. This is why a third run hasn't been decided on or announced, dealers haven't finished selling off the second run.
The official word from Takahashi in Japan is that it's unlikely there will be a third run anytime soon. They might produce a third run eventually, but not right now.
BTW, if you have a DL from the first run, you might want to hold onto it, these are much more special than you might think. The first run were like the much older FC-100N f/10 version, they only planned on making the one run at the time and wanted them to be something special. These were tested and finished by their best opticians and they wanted them to be as good as they could possibly make them. This isn't to bash those from the second run, it just means the second run was produced to the same extremely high standards as all of their beautiful refractors. I very much doubt anyone would be able to tell the difference between the two runs just looking through them unless they had good seeing and performed careful star tests.
At any rate, if you were wanting a DL, now's your chance. If you have one from the first run, you lucky dog! :-)