Sure, but I find the problem isn't competing against twenty somethings once you're hired (could be done with one lobe tied behind your back, haha). It's getting hired by them at all, and very difficult if you're not "internet famous."
Having recently interviewed lots of developers (in NYC), my experience was that there's such a shortage of senior and even solidly mid-level talent out there currently that an employer would have to be crazy to turn down anyone for non-merit based reasons. We would have hired a 300 year old sea turtle if it could get the job done... internet fame definitely not required.
Perhaps the problems are more at the margins (junior level devs, choosing between people of similar ability), but unless the market changes drastically, I can't see a competent engineer having too much trouble regardless of age, at least in locations with a big enough tech scene.
