Social Security already is insolvent. It has been insolvent for a decade now. The so-called 'solvency' that the article above claims is based on assets that do not exist. The fact is that more money is paid out to recipients (30% of which are below retirement age) than is collected from workers in taxes. This requires tax revenues from the general fund to be diverted to Social Security to make up the difference.
What requires funds to be diverted from general revenues is the fact that the prior excess revenues from the social security income surtax were not set aside, but were instead "lent" - cute use of that word, btw - to the federal government for general expenditures. As a result, the only way to recover the "invested" - also a cute use of that word, btw - funds is to expend general revenues from the normal income tax (and other federal sources of revenue).
Had those prior-year excess revenues in fact been invested, then liquidating the investment to cover the excess benefits now would not have required dipping into general revenues.
It's all, at bottom, a glorified Ponzi scheme that would have made both Bernie Madoff, and ole Charles Ponzi himself, proud.
That being said, even if the prior-year excess revenues had been invested, rather than spent by the federal government itself, the program would, on its current trajectory, become insolvent sooner or later.