Four Five Beta One is what they call it.
On Feb 25, 2015 Mike Schroder , a core committer and WordPress Platform lead announced the release of WordPress 4.5 Beta 1 on WordPress.Org
Though still in development and not recommended to run on Live sites, WordPress 4.5 is planned to be released on April 12 this year.
4.5 comes with some cool enhancement in the Core, which include:
1) Responsive Preview of your site in the Customizer:
Now you can look how you site will look on Phones, Tablets and Desktops right from your ‘Customizer’.
It comes with a flexibility of testing the responsiveness of the site without actually publishing the content.
2) Theme Logo support within Customizer:
Another enhancement on Customizer, now you can add a site logo from your Customizer panel.
In core, it’d be a theme mod enabled via
add_theme_support( 'site-logo', size ), rather than storing the logo persistently across themes. – Mike Schroder
This is a great move from WordPress and the plan is to release a new version of TwentySixteen theme along with this feature on WordPress 4.5
3) Inline Link Editing:
Inline link editor enhancement will give user an ease to edit the links in the posts from within the editor.
When user choose to add/edit any link, he’ll get an edit box right in the post editor, which makes it easier to add/edit the links.
4) Additional Editor Shortcuts:
To make your life easier, WordPress core team is coming with Editor shortcuts. You will be able to edit post contents with short-codes straight from the editor.
Eg: ‘…’ for code , **…** for Bold and *…* for italicize.
5) Comment Moderation Improvements:
A better layout for moderating comments which will give a preview and the formatting of the comment.
6) Image Optimization:
Images will be optimized to decrease RAM usage on servers, this will reduce image size up to 50% while keeping the visual quality almost same.
Where can I download 4.5 Beta from?
WordPress 4.5 is still in Beta testing phase and is not recommended for Production sites yet.
You can download 4.5 from Here (Zip)
Where can I see what all has changed in the Core?
All the changes proposed in 4.5 are listed here
What if I find a bug while testing 4.5?
You can start playing on test environments by installing WordPress 4.5 and if you feel you found a bug you can report it to Alpha/Beta Testing area
Also do check the list of known bugs.
Let us know what you think about this next release from WordPress.