It was rumored for some time so it doesn't really come as a total surprise, but now it's pretty much official that there will be no DVD release of Windows 10.
Microsoft's Windows 10 operating system will be available in retail stores in the form of USB drive versions, you can already pre-order these on Amazon. The Windows 10 Home and Windows 10 Pro USB drive sticks go for $119.99 and $199.99, respectively.
Ditching DVD drives makes sense as optical discs are no longer widely used and a lot of systems, especially thin laptops, no longer have disc drives.
The preferred method remains digital distribution of course, if you have Windows 7 or Windows 8.1 you'll be able to upgrade to Windows 10 for free. The launch date is July 29th but it's going to take a bit longer until everyone gets it, if you accept Microsoft's free upgrade you're placed in a queue and Microsoft will be doing daily rollout cycles so they have time to adjust things in case problems arise.