Nalbandian's girlfriend his pregnant and probably the two main reasons why he quitted are to spend more time with his girl and prepared for the Davis Cup too. I don't see David playing tennis for a long time (mentioned that he might be retiring after Miami MS according to what happens in Davis Cup)
He's going to play all of the next season. That bit about possibly retiring after Miami was obviously a misunderstanding.
What he actually said was that he has his schedule planned until Miami, the rest he still has to see about.
(Which is also going to be matter of ranking and wildcards.)
It's all about not wanting to switch surfaces. If the DC tie was played on hardcourt (which Jaite and the AAT offered for the sake of getting Delpo to play) he would've done his pre-season on hardcourt and played the Australian Open.
Now that this won't be the case, he'll do his pre-season on clay.
Davis Cup is the #1 priority for Nalbandian. That's nothing new and neither is him, skipping a Slam for the sake of it.
I can definitely see him retiring soon.
Probably at the end of next year. Though he still refuses to make a clear statement about it.