Yes....most of the airplanes at my company came with CF6-80C2B5F engines installed, rated for 62,100 lbs of Boeing equivalent thrust. Over time, they become de-rated to CF6-80C2B1F engines which are rated for 56,500 lbs. The decisions regarding when and why to accomplish these de-rates are usually made by the engine owner/lessor, to the best of my knowledge.
Maximum N1 & N2, 117.5% and 112.5% respecitvely, remain the same for both B1F and B5F variants. Therefore, one might conclude that for a given N1 value, less thrust is being produced by the derated engine.
So...does the thrust produced by engines at a given N1/EPR degrade over time? Yes, I would say so. Does this happen appreciably even prior to the de-rates being established for a given engine? I do not know for certain, but logically one would say yes, a new engine probably performs closer to rated specifications than an old and worn out one. Wear and tear on the engine's blades likely leads to less efficient compression and therefore less thrust being produced at a given RPM. An engine mechanic would be a much better person to ask this question to, since they are undoubtedly the ones responsible for monitoring engine performance and making sure the engine is overhauled or replaced once it degrades beyond limits.