Microsoft first announced that Edge was coming to iOS and Android in October, launching a preview shortly thereafter. Interestingly, when the iOS version was made generally available, it still didn't support Apple's flagship iPhone X, or any iPads. iPhone X support came in December, but we're still waiting on iPad support, a feature that was promised from the beginning.
Microsoft's Sean Lyndersay tweeted recently that the feature is indeed coming soon. It will be available in preview beginning in early February, after which the company will collect feedback from users before making it generally available.
Of course, there's nothing stopping you from using Edge on your iPad today; it's just not an optimal experience. Apple allows users to run any iPhone app they want on an iPad, except it's just blown up in an awkward way, and device rotation usually doesn't work so you're stuck in portrait mode.
It's unclear what features, if any, Microsoft plans to add to its in-house browser for the iPad, other than the 4:3 aspect ratio and larger screen. When the company first announced Edge for Windows - then only called 'Spartan', a throwback to Halo - one of the key features was the ability to mark up the web with a pen. This seems like something that would be useful on an iPad Pro, but we'll have to wait until next month to see.
There's no easy way to sign up for the preview if you're not already on it. If you are, keep an eye out for updates via the TestFlight app.