Hey @yvesriel, I can give you some more information on this topic.
Since Dave’s post back in November, we have sent out some more information in December about our upcoming Alpha program. The Alpha program is being used to provide information and time for app developers to use the new APIs and see their apps in the new issue detail view before we start rolling out to customers who have apps installed. You are correct that you cannot see apps in this new view at the moment (it’s only out to some customers and only on the board & backlog views).
Be sure to sign up using the links below! This will be started soon, we are wrapping up some development work, API documentation, design guidelines, and lots of examples to make it very easy to make changes.
You can read more and sign up your cloud dev instance here:
blog: Alpha program for the new Jira Cloud issue view - Atlassian Developer Blog
Community forum post: Sign up to develop against the new Jira Cloud issue view - #4 by pvandevoorde
Finally, the feedback from customers has been overwhelmingly positive but at the same time we have learned a lot about different preferences in how people work and still have things we need to address. We are using this feedback to continuously improve the design model and prioritize how we build out more complex functionality.
To be transparent with you about what we are seeing re: your comment on the modal view on the boards, the majority do really enjoy it. However, we do have a smaller group of users, who typically are looking at many issues and clicking through a lot, preferring the sidebar for the reason you describe (they do not want to have to close the modal to move to the next issue). We will address and provide a solution to these use cases in the future, but we are currently focused on getting ecosystem support and performance 
.
I hope this provides a window into our thinking here and next steps! I look forward to getting your feedback during the Alpha program.