Good topic!
I was also thinking the same and have an idea...though may be a little extreme..!
When Shyam finds out about Payal and Akash, may be he'll kill her?? It might not be his intention to do so, but just to do something to stop the marriage, but inadvertently kills Payal?
It would be a great way for the story to progress. And even more so if Arnav learns of his Jija's dual life, eventually leading to his and Khushi's marriage to save his sister's.
There has been recent buzz that a Deepali has been approached for various shows, including one opposite Akshay. Not sure if this has been confirmed either way, but if it has, CVs may have something like this in mind...
After Payal's death, Akash will be too upset to stay in Delhi and may decide to start afresh elsewhere...making a feasable storyline for his departure from the show...
The above is just an idea...my imagination running wild...but certainly a possibility!!