For the sake of bitcoin, I sincerely hope that people holding many tens of thousand to hundreds of thousand coins cash out over the next year or so, and that they do so in a way that distributes their coins among a large number of people. Let's get this over with. The project isn't going to be able to move along and gain the level of trust it needs until the risk of enormous dumps is significantly reduced.
I don't think there is any hoping required. This happens naturally because hoarders are people and they have different mindsets. Some will be happy to sell some or all of their coins when the price has increased 100%, some will wait for 1000% and some for 10000% or in some cases even 100000%. Some of them simply invest for 2 years and exit. Some will never sell but will use those coins gradually once they become more usable.
One thing is for sure, only a very small minority of users will be able to resist the temptation of not selling coins at some point while we go towards the price of $1000, for example. The distribution of coins is very likely to get better and better as time goes on. But even if this issue is reduced, it's never removed. As with any other currency, there are always big players who can affect the price. Even now someone with millions of dollars could buy a lot of coins at any time and if that person happened to be one of the so called super-hoarders, his actions could have a significant effect in the long term future.
I also think that the people who actually have the patience to keep money in bitcoins for years without worrying about the short term volatility, they are smart people. It's very unlikely that these people would suddenly just sell everything in year 2020 and crash the market, they would know better. It's the speculative types we need to worry about just like we've seen with Bitcoinica recently. But their effect will undoubtedly get smaller through time once the market cap is larger and there are more large competing speculators.