No, it is not millions of people.
BILLIONS of people will be displaced if the water level rises even a moderate amount. Here is a fun toy It only covers part of the world, but the hyperlinked areas are illuminating.
Notice how even a small increase will shut down some of the most populated regions of the world as the cities are right on the coast. China will likely see a billion displaced. India might have a a half billion displaced.
The US might see only around 40 million displaced, but having New York, San Francisco, LA, Houston, Miami, and a bunch of others at least partially underwater or seasonally flooded will be difficult enough. That means rebuilding the infrastructure for millions of people in the United States alone. When Hurricane Katrina type flooding becomes an annual event due to higher sea levels, continuously rebuilding the cities will not be an option. People will be displaced and the annually-flooded buildings looted and condemned.
Wars are very likely. Look at India losing about half of its useful land and displacing so many people; suddenly all the land to the North looks mighty inviting, even with their arsenals. The Nile Delta flooding could displace seven million; there isn't much nearby green on the map for them to move to within the country. Netherlands probably won't survive as we know it, so what about erasing the line between them and Germany? That one at least has a chance of being somewhat civil.
When you combine the stress of losing a lot of land, some countries having their land vanish almost completely, and billions of displaced individuals, tensions are going to skyrocket very quickly.
Long-term real estate investors and the filthy rich have been picking up tracts of land in places that are elevated, cool, and have fresh water sources. Most people haven't really noticed.