I don’t think they are going to give us a sad ending. The PH and writers can’t be that cruel. They know RiAnsh is an emotion for us and how attached we are to them. They already know how upset the FD is after knowing that the show is ending abruptly so I doubt they will play further with our feelings by giving a sad ending.
Also, was it always supposed to be riddhu and Vansh or is after their growing fandom that the CVS thought to make them the main couple rather than Kabir and riddhu?