I just thing that Williams is on the downward trend that we saw Lotus, Brabham and Tyrrell go down on a path to bankruptcy or being bought out.
I'm absolutely sure Williams will not go bankrupt or bought out in the next 10 years. They already have budget quite a lot of bigger than teams like Sauber, Force India, Toro Rosso and that without going into the slightest debt. They've secured quite a lot of sponsorship deals recently, they have a special payment from FOM, their activity outside F1 is growing each year. so from financial point of view, they're completely secure. They'll not go bankrupt and it's no point of selling the team as well. Maybe they don't have a possibility to gather a championship-winning budget, but they have an upper-midfield budget gathered without the slightest problem. People like these kind of comparisons but each team is different story and there is absolutely nothing to suggest Williams will disappear from F1 unless we see some fundamental changes in F1.
About Williams being seen as a dark horse- I have to agree with many here. Before every single season many people predict them as a team to make the biggest problems, but it rarely happened. And even if they came with an exceptionally good car (2009 and 2012), they failed to capitalise on this and secure a good result in WCC and repeat their performance a year later. It requires to be naive to believe they'll seriously challenge the frontrunners now.
On the other hand, with their budget and resources, I'm sure Williams will start finishing within top6 in WCC on a regular basis soon. They have to. They're clearly stronger than Sauber or Force India commercial-wise, including facilities and technical possibilities. They can afford to outbid some engineers from other teams (for this year alone they've brought Symonds, Andreassen, Nelson, Wheater, Whitehead, Wilson and probably Smedley, among others, they've undoubtedly gained more engineering strength from other teams than lost to them), so each time they underperform big time, they'll be making changes and once they'll get it right.
Anything higher than 6th will be a big success (unless Lotus is eliminated from being competitive due to financial reasons anytime soon), but anything lower than 6th will be a disappointment and will not reflect team's potential. They know it in Grove so they'll react to ensure the team finishes in top6 in WCC on a regular basis, because they have everything to make it happen.