On balance, I agree with you. you have to figure areas of law involving tax, financial services, and medicine will benefit most from the retirees. this country is going to undergo some major changes in the coming years. regardless of what happens, everyone will benefit from the extra options a law degree will bring.
its also worth noting that the workforce will be getting a lot smaller, which should improve the employment market (or offset jobs going overseas). But there will also be a huge burden of entitlement funding on working people. The government may tweak the tax code to encourage workers to work longer or do numerous other things, but as it stands now there are big problems ahead.
if you want to see a similar model of what could happen, look at japan which has an aging population and has been suffering for several years as a result.
Japan's problems were based on other issues. Mainly their monetary system was corrupt, and their economy lacked diversification and too geared towards consumer goods and export oriented. These factors led to their economic problems and recession, which led to more unemployment and decreased real wages. You add the fact that, yes their population is aging, so people WORK LESS and make LESS MONEY, and yet have to support those old people. It just made things worse. Their economy was not diversified to the point where they could actually take advantage of the old people retiring or being a market force.
Yes, the old people in this country will soon become a burden. Health care, social security taxes, etc. will burden the young people in the form of rising costs and increased taxes. Yet I also would argue that because these people can be clients and also because of the new economy that can emerge because of these wealthy people spending money in retirement, lawyere will make more money and have more jobs, thus being able to take on the extra burden of "paying" for the elders. Of course, the only problem I see is that the potential problems above could lead to inflation, as costs go up and wages will struggle to keep up with the majority of jobs. Though I think lawyers and other skilled occupations will be fine and even benefit, there might be an increasing gap between the haves and have nots in the future...