Amasia is a possible future supercontinent that could be formed by the fusion of Asia and North America. This would eventually be hit by Australia, then the rest of the continents. The main difference between Amasia and Novopangea is that Antarctica remains on the South Pole, and South America rotates nearly 90º, taking Antarctica's place in Novopangea.
According to Wikipedia, "A February 2012 study predicts Amasia will form over the North Pole, in about 50 million to 200 million years." The wide range of times is due to the unpredictability of the rate at which continents move. It is presumed to form in the northern hemisphere because a pattern emerges showing that supercontinents form about 90º away from the previous supercontinent. Thus, assuming that Amasia forms 90º away from Pangaea, it should end up roughly around the North Pole, centered on Greenland. Amasia is one of the most referred to future supercontinents, along with Pangaea Proxima.
Compared to other supercontinents, Amasia is a contender for the most plausible. However, one problem with the Amasia layout is that Antarctica barely moves, which, given enough time, will be forced to move north due to plate tectonics. However, this does not mean that Novopangea is more likely, as this specifies that Antarctica will end up between the Americas, Asia, and Australia. A possible reason for the static layout of Antarctica is that not enough information is known to be sure which direction it will travel in the future. However, if Amasia occurs sooner (as in 50 to 100 million years from now), rather than later, Antarctica will likely not be a part of the supercontinent. Put up against Pangaea Proxima, we can say that there is more evidence for Amasia forming, since no one has proven that due to a mid ocean trench the Atlantic will begin to close. Interestingly, in either Amasia or Novopangea, the global ocean is mostly the present day Southern Ocean, and only partially the Atlantic, as most continents are moving northwards.