Anu,
The reason they may show miscarriage is for two reasons:
1. Vikram is in jail and they have decided to let go of him for now. So, if Vishaka doesn't have her baby, she would be more vengeful towards Dev and may now even join hands with Mrinalini. She can't use Radhika too much as Radhika is now aware of her true colors and is no longer the gullible Radhika she used to be. Also, this time Vishaka's actions of ruining their time together has ended her feelings of unnecessary obligation. I think Radhika was more angry with Vishaka because her actions hurt Dev so badly and ruined his much anticipated moments. She is used to sacrificing her happiness for Vishaka. But, this time it was also Dev's happiness.
2. As Gur wote they are showing Holi promo of Dev and Radhika where they are not very happy. It may be because Dev unintentionally caused Vishaka to lose her baby. So, maybe they have to bring her back to Delhi to take care of her. I don't think they will bring her back to PB yet.
3. They are showing some sort of unhealty attachment on Vishaka's part towards her baby. She is acting as if all her problems would be over once the baby is in the world. This is somewhat inconsistent with Vishaka's character as she is selfish enough not to ruin her figure or whatever for a baby.
However, if Vikram is still in the picture and there is a connection to Waaris issue, then they may not show Vishaka miscarrying. But, Radhika and Dev still feeling obligated enough to take care of Vishaka for the sake of her unborn baby. As Shastriji would be mortified to hear about Vishaka's illegitimate child, Radhika would be forced to deal with issue along with Dev. That is okay as you do help your bad siblings if they are in trouble. After all, this is a soap and can't just goody goody moments.
My wish for Holi is just one nice holi song between Radhika and Dev as their relationship is now open. But other than that, they can deal with Vishaka and others if they are united.