Since you already started with scrollable area inside artboard, it would be awesome if we could define sticky header. For example, one page website has a lot of content, but I want to create sticky header so when I scroll down, it stays at the top. Maybe you could add the option so we can define the group and assign the sticky header option to it. That way on any artboard we can just assign that option to it and that's it.

Support for simple animation.
Example: Show/hide a slide or push menu

This would enhance a demo and engage prospects that are familar with common application patterns.

Have an ability to display a grid/guides mainly for web design use cases.

Define a scrollable area within an artboard

This provides real-world app use cases, such as a table, slideshow, or iOS dropdown lists.

Need Little bit tapping/hover effect on list/buttons/links during presentation to client. Its give an actual working product feel and help to make decision.

rollover, mouseover

Provide the ability to change multiple objects/elements within a document and/or across artboards.

Example: Ability to increase font size within a button across all artboards (without multi-select)
This is similar to increasing font size within a repeatable grid—all increase.

Another example: replace/swap a theme color throughout the document.

Hi there, currently the only interaction is a page switch with some easing functions, but when you click a button, it would be nice that you van select a artboard that you can use as a "overlay" over another artboard. So that way you can create lightboxes in your protytype.

Similar to Edge Reflow, it would be great to have the ability to prototype responsive design ideas with a fluid, flexible canvas. Web designers need a good tool for this there really isn't anything out there to test out responsive design solutions.

Support to import a video or animated GIFs to simulate animations or even playable video.

Import Photoshop file with options to select layers and/or artboards.

This would increase ease of use and workflow, so a user is not always switching between apps. Import options for layers, artboards, or even layer comps, would also cut down a lot of rework.

You can easily make text bold or italic in XD, but not underlined. There should be an Underline style or toggle button for creating designs with links, etc.

An ability to drag out persistent guides to an artboard and have other objects snap to it

I remember, I have seen this presentation at Adobe MAX 2015. Where we can use dummy / Sample data for content such as Name, city, country etc (Please also think to add lorem ipsum dummy paragraph if possible).

I would love to know, is there any plan to integrate that concept in near future. Its a really great functionality and time consuming important feature for us.

Ref - Design with Data - Adobe MAX 2015 - Sneak Peeks:
https://www.youtube.com/watch?v=e8ebPSJR3U0

I would like to share my full document to my team in order to communicate all specifications I added. This would help them giving a bit more context to the prototype and also be able to see all the different states of a pattern to build.
Maybe save as a PDF file or also online?

1. Ability to have a single object (or group) break out of its artboard and cross multiple artboards within a single prototype. The simplest use case is the creation of a global navigation bar that spans across multiple screens. This object's interactive elements would also work across multiple screens as well, and any edits to this object would update across the rest of the screens.

2. Easy interaction management and editing. Also provides consistency with consistent elements within an experience.

This would make it easier to use the assets created in other Adobe applications.

Import Illustrator file with options to select layers and/or artboards.

This would increase ease of use and workflow, so a user is not always switching between apps.

It would be great to Export Prototypes as pure HTML Projects. I am working a lot on Multiscreen apps, where I mostly use Serveal Webcontainers Running on several Screens, to develop those Applications.