I know "Blue Bloods" has been running on Ion Television for a few years now and they were on late night on our NBC affiliate here in Anchorage, so you could be right on the syndication part. I think "Blue Bloods" will end when Selleck pulls the plug there and I actually expect that within a year or two.
An interesting note about the Five-0 finale: it will air two days shy of the 40th Anniversary of "Woe To Wo Fat" which aired April 5, 1980.