Originally Posted by
LineageRazor
As others have said, it's pretty much inconceivable that we will become unable to return to the Source at will - even for just a short space of time. The only question is how much time they'll bother to spend explaining how it's possible. Personally, I consider it very likely, once we get to the First, there will be a cutscene that explains that the Crystal Tower has been established as a conduit to allow easy transport between the Source and the First - all before we're able to take even one step onto the First Shard while under our own control.