A lot of them seem to have gone to Cape Cod. Sunday night's 60 Minutes had a fascinating segment on East Coast great whites. They have become thicker than flies off Cape Cod, apparently responding to the great increase in grey seals. It showed video of them cruising right off the beach, just like they were in Capistrano Beach a couple of years ago. Guys were out of the end of bow planks sticking tags into them, and seals were lined up at the water's edge. They had one video of a seal leaping out of the water with a shark after it, and then finally catching it. They also showed one leaping up and almost biting the plank that a tagger was standing on.
They say that the tags show that they migrate clear down the East Coast and into the Gulf of Mexico. They also go out into the middle of the Atlantic and dive to 3000 feet, but they can't figure out why.
And then it moved to Nova Scotia. Apparently there are lots of sharks up there, even though no one knew it until recently. They had a special big boat rigged for research. They would hook a shark and get it up beside the boat, and then raise a massive platform that lifted the shark out of the water. Then a team would jump down, stick a hose down the shark's mouth to run water over its gills and do all kinds of stuff- take tissue and blood samples, insert a tag into its abdomen, drill holes through the dorsal fin to bolt on a tab that transmitted position every time the fin was out of water, etc. Their goal was to get it all done in 15 minutes max. Then the platform was lowered back into the water and a guy would herd the shark off the end and make it swim away.
If you can see it, check it out.