dd is 5, and just had three crowns and five fillings. I was shocked too - she eats very few sweets, brushes well twice a day, drinks water etc.
Her problem was teeth that are very tight fitting (close together) and the inner surfaces are obviously unbrushable - we didn't think to floss a child of her age, and the dentist couldn't see any problems at check ups until it was too late. THat, and genetics, poor thing!
If she'd seen an NHS dentist, they would probably not have bothered with the crowns and just extracted - thats what I was told, anyway, not sure if its true. As it was, we were lucky to have them done relatively cheaply and dd has all her teeth and now flosses nightly.
There will be no future consequences, necessarily, but if the problem is genetic (ie weak enamel) as opposed to due to prematurity or bad diet or poor hygiene, then the tendency towards decay will stay - again, so I was told. In dd's case, she will always need to be reasonably careful and floss like crazy