Indeed, but it might become less of a gusher over time for other reasons -- mostly due to a reduction in foaming agents like proteins and extracellular carbohydrates. The lysing of the yeast often liberates proteases which can slice up long-chain proteins (some of which might be liberated during the process of lysing itself, so the change in protein concentration might be somewhat non-linear). Yeast cells themselves may bind together and usually crash out of solution given enough age. Extracellular carbohydrates (like the beta-glucans that cause ropiness via pediococcus) can cause even reasonably carbonated beers to get real gushy, but Brett will eat them during extended ageing.
I suppose that over really long timespans, they might lose some carb through really slow mechanisms that leave most other things intact, too. Like diffusion through the cork or something.