Re: Series 7b screencaps *Spoilers*
If you think about it, They could pretty easily get away with treating a 2014 series as the anniversary series as long as they air it before the 51st anniversary. After all, "Celebrating 50 years" works a lot better after you actually have a full 50 years to celebrate.
"There is no reason why good cannot triumph as often as evil. The triumph of anything is a matter of organization. If there are such things as angels, I hope that they are organized along the lines of the Maffia." - Winston Niles Rumfoord.