Personally, I don't see how such a model can work. By using this model you're spending millions to make a big game like LotR and then hoping that enough of your customer base will pay for new content. But making new content itself is costing money and you haven't payed off the initial investment yet. I don't see how you wouldn't always be chasing your tail with such a model unless your later additions are going to be really cheap to make and expensive to buy, but why would anyone buy that? Just because the initial offering was free doesn't mean people are going to be willing to pay a lot more minor enhancements later. If anything, you're probably escalating what it takes to spend money.