It looks like "modern pages" are now rolling out to the tenants with the preview options on. You can still create Wiki Pages and Web Part Pages in addition to the new "Site Page" type. Here's both the new and classic Site Pages library “New” menus.
The new pages have the "warm and fuzzies". Click to enter a page name. Note the Publish button. New pages are left checked out until "published". Major versions are enabled on the Site Pages library.
While web parts are not listed yet, you can add some "widgets" to the new pages. (Hey! There's a Yammer thing there!)
So… stay tuned to see what will appear next!