Leman State is at the centre of Zemuria, so probably east of Remiferia and north of Calvard. We know the Holy City of Arteria is also in central Zemuria, probably a city-state in Leman, similar to Vatican City. The other nations we know, North Ambria and Ored, are respectively north of Erebonia and east of Calvard. There's even more than that, but nothing that been mentioned by name so far.
So there's still a lot of ground to cover and Kondo has already announced that once the story in Erebonia is wrapped up, the focus will move to Calvard. The reveal that the online spin-off, Akatsuki no Kiseki, will partially take place in Remiferia has me believe that none of the main series will focus on Remiferia - or North Ambria for that matter - and that we'll continue to move toward Zemuria's eastern half after Erebonia's arc is finished.
Well, we also know that series as a whole passed its halfway mark as of Cold Steel II.