I thought it would be fitting, but you never know. Celebrating 5000 episodes isn't as special as celebrating 30 years. So perhaps they won't waste their time with the oldies until February to give them their chance to shine.

There's a difference between counting down to Christmas and a episode of Eastenders.

Funny how the 5000th is just near the 39th and Emmerdales 42nd and 7000th were at exactly the same time, I think thats why only one is celebrated, EE's 4000th was just after the 25th also

You're working off the assumption that the NYD episode was always intended to be a one hour episode, it was more than likely two merged together, with both written by Carey Andrews. Both would have been made to air on NYD though.

The Christmas eps are usually merged too because you can see where the original doof doof moment would have been. They double up at Christmas and don't know how the BBC are going to schedule the show months in advance, in the past both the Christmas and NYD eps have aired in two parts or been merged into one, as there's always the faint chance of a two-part airing its probably easier to produce two separate eps rather than a single hour one that wouldn't necessarily have a natural doof doof point half way through, and would need to be cut in half if the BBC did decide to run two episodes.

The NYD ep being two eps merged together would explain the Radio Times skipping an episode number.

EastEnders always do extra episodes over Xmas. Last year for example it aired every week day for three weeks. 3 of those days saw double episodes.