Yes, plasmas suffer from worse burn-in.. though i was under the impression plasma tvs are becoming less and less susceptible to this problem. It is possible the problem will be totally rectified in the future.
All phospher type displays are vulnerable to ghosting and image shadowing referred to image burnin. Newer techniques are geared at motion adaptive which is designed so as not to be detected by the human eye while still moving any still image just enough to prevent this. A good plasma tv shopping that goes into further explaination is seen at http://www.plasmatvbuyingguide.com/plasmatv/plasmatv-burnin.html
Going from lcd to plasma would be like going from a new 4x4 to a Model T! There are some new flat screen and lcd tvs that will work out far better. With HDTV becoming more and more popular you have to take this into account as well.
Right now, the only place plasmas reign supreme to LCDs, is tvs about 42", they work better in larger sizes. The only other plus is their very very high contrast ratios. But as LCDs get better and better, these pluses may evaporate and leave LCDs the victor.
i realize you're talking about flat screen panels, i'm saying that your better off $ for $ getting a rear projection lcd vs. a flat panel, and that the larger flat screens are popular right now because they're new, and "cool"