I agree with shayma's message. Check the site that shayma provided in the post above and check if the visa has been issued. The same thing happened to me and it took about a month to receive the call back for pickup. Apparently the site said the visa was issued and the embassy did not have the folder package put together for pickup. All will be well, it is just a matter of time for them to call you.
I'd first like to thank you all for your assistance and helpful insight.
Livetolove- I am sorry to hear that after waiting so long that your Yemeni friend was rejected at the US embassy in Yemen. It is unfortunate, but this is common at the US Embassy in Yemen as my brothers also had problems years ago when they applied for their wives and encountered insensitive employees, inconsistent processing, and required numerous hard to get visits.
Based on your friends dilemma, I will not hesitate in completing the DS-260 sooner rather than later.
To me, it seems that based on your response as well as the response from H&A&N, the typical wait time is currently approximated at around a year after NVC has completed the case. Unless current conditions change, for us, this would mean approximately another 4 to 5 months which is unfortunate.
My heart to goes out to all those like me during this long and difficult time of wait.