Growing up, I always viewed the OED as a stodgy old dictionary that was rather resistant to change

It's not, though, and it really never has been. It's slow to change, because they rarely release new editions, and before the Internet it was uncommon to see new entries outside a large library until the next edition was released. But the OED has always been descriptive -- an entry in the OED does not mean that the editors approve of a word, only that they received sufficient evidence that people were using it.

The official phrasing is that it "is a descriptive dictionary, not a prescriptive one. It does not attempt to set a standard of correct English: it records impartially the uses of writers from every part of the English-speaking world and at every level of the social or literary scale."

So "bling-bling" and "blog" belong in the OED, and whether or not they are included in a future edition depends essentially on manpower and allocation of research resources.

(For the record, the opposite of "descriptive" is "prescriptive". There are few if any prescriptive dictionaries these days.)