Wading into a minefield with that question, but I'll answer it anyway.
As far as the speculation surrounding this is concerned, there's a short answer and a long answer.
The short answer is, yes, going with the friendship route ends any and all chances to get with them for the remainder of the game, be it with both of them or just one of them. The long answer is, maybe not, and that whilst going with the friendship route ends it now, one or both of them might gravitate back to the MC if their relationship hits the skids again.
The long answer, however, is an unpopular view around these parts with some folk who feel that if that were to happen, it would undercut the seriousness of the choice of Ep 4. However, there are a myriad of different ways this story could go, especially when it concerns the relationships between different characters, and it's quite easy to imagine scenarios in which one or both of them might come back to him. So to say it's completely over already feels a bit premature.
Obviously, players don't have to get back with them, but there's no harm in keeping the options open for those that wouldn't mind that, especially if it fits within the story.