The last supercontinent was Pangea Asia, Europe and Africa are what is left and they are continuing to break up. The next one will meet where the Pacific plate now is.
So this starts as a rift, then a valley, then an inlet, then that will widen into an ocean, and then the barriers between oceans will disappear.
So yes, this will be a sea before it is an ocean. But it is also correct to talk about it as the birth of a new ocean. (The Red Sea is also on its way to being an ocean. It is just farther along. And the Atlantic is farther along still.)
Is there evidence for any changes in convection currents?
i.e. what do we have to go on, besides back-extrapolation of observed drift (happening today, and in "recent" geologic past, e.g. reversal of magnetized direction)?
Why should the continents recombine into a supercontinent, rather that drift arbitrarily? Is the idea that, sooner or later, a traffic jam will occur, where first two bang into each other and can't move, creating a larger obstacle, which another then collides with... but since there's some process for a supercontinent to separate, what's the neccessity for this process to not tear apart the collided continents before a full supercontinent is formed?
Unless I'm wrong, and the tectonic plates existed and were moving long before the oceans did?
http://csmres.jmu.edu/geollab/Fichter/Wilson/Wilson.html
For further reading I can recommend 'Supercontinent' by Ted Nield.
https://en.wikipedia.org/wiki/List_of_supercontinents#Prehis...
Seems to indicate otherwise, but I'm certainly no expert on geology or whatever sub-specialization is concerned with plate tectonics and history of them.
Here's the map image alone: http://cdn.mg.co.za/crop/content/images/2015/03/31/easplitma...
This is where the explosion was https://www.google.com/maps/@12.642073,40.5202369,1118a,20y,...
No the rift is here:
But, yes, the initial body of water that will form will not be what anyone would characterize as an ocean.
Also a story like this without a map is very annoying; my best guess as to where it is is here:
https://www.google.com/maps/@10.1384475,40.4893819,818636a,2...