Yeah, I don't know where they got that number from; it was just quick googling from me:
http://www.taalcanon.nl/vragen/hoeveel-dialecten-heeft-het-nederlands/
As for the ABN thing, I don't think it will converge to a single language. There are actually people who speak their local dialect in the village and a more ABN-ish language when there are 'outsiders' in the room. As a result, it's funny to call someone out for their dialect/the area or province they come from, because you can always here differences in articulation. Fortunately, there's one uniform writing language xD
It's a fun thing, which is recognised here btw. In 2005, two Dutch rappers wrote a hit song called 'Het Land Van' (The Land Of...), in which they sing about the characteristics of the country and its people, and one sentence is (translated): 'I'm from the land which you can traverse in three hours, with a new dialect every 10 minutes'.