Lorne Balfe's music on the Revelations soundtrack put Kyd's to shame. His work was feeling stale at that point. The main theme for AC3 was outstanding as well. AC2 level work wasn't coming from Kyd again.
AC3 had a couple of nice tracks (which is more than I can say for Black Flag), but it was mostly uninspired background noise, and as for Kyd's work feeling stale I'd put much of the blame on Ubi for sticking with Renaissance Italy for three full games. In any case, though, I'd love to see what he could do now that Ubi's moved on to new backdrops.