Semiconductor International published Chipworks article talking about how HD video feature affected DSLR sensor design. The article analyzes quite significant changes in Samsung sensors used in Pentax K-7 (HD) and K20D (non-HD) and Panasonic DMC-GH1 (HD) and DMC-G1 (non-HD) sensors. Chipworks also mentions that Nikon uses its own designed sensors in its recent DSLRs, rather than outsource them to Sony. Canon DSLR sensors are said to be very stable design-wise and have little evolution over the last 3 years, with most performance improvement possibly coming from the Digic ISPs.
Update: Chipworks blog has an expanded version of the article.