I don't think I will improve migration speeds that much for this release. I tried to average migration speeds so that humans would cover a continent in around 200,000 without any kind of transportation technology, based around the fact that it took around 280,000 years for humans to cover Afroeurasia. But this is very flawed. In reality, it took humans the bulk of that time (230,000 years) just to get out of Africa. Then, they expanded over the rest of the supercontinent in just around 50,000 years at very different speeds (Europe took only 8000 years to be fully settled by early humans according to recent models). To really make a decent model I would have to make migration dependent on multiple factors other than just terrain accessibility. But I don't have enough knowledge to properly model that at this point.
I think the best I can do for this release is make migration events happen more frequently, this will ensure that continents are covered much faster.
Viewing post in Done with Decision Mods, Again (for now) comments
Yep, I need to also work on sea migrations to handle situations like that. Because sea migrations can speed up colonization a lot, but they are also very dependent on technology and external factors like ocean currents. For example, the Polynesians were able to colonize many distant islands because they mastered boatbuilding and navigation at a very early stage, but they preferred navigating against the current to ensure that their failed exploration voyages could be returned from. I would need to take into account stuff like that in my model.