I am sure for a while, he will be stupefied, because it is the most natural thing.
You think someone's dead for all these years and then she suddenly pops out of nowhere in flesh and blood, especially when she is someone with whom you had history, is going to be a little emotionally draining for Neil.
What I also think is, the shock, the confusion, and the confession, would all take a backseat for a while, as Neil would somehoe get more involved with the investigation of Rang Mahal/ Raghu Pandit/ etc.
It is okay. I don't mind.
As much as I long for AvNeil's confession, I don't want it to be a hastened event.
Neil should definitely clear his head and realize for the final time that No, he doesn't feel a love so intense for Juhi, the way he feels for Avni.
And only then should he go forth, give Avni that ring, and make her his in all senses.