The fact that you haven't received the update yet has absolutely nothing to do with Dell not having tested Windows 10 on your machine. It's not like Microsoft actually checks your machine type and the manufacturer's database of systems for Windows 10 support, those are two completely and entirely separate things, like trees and space ships
That said you might still be able to run Windows 10 without a hitch. I've installed it on a Lenovo Thinkpad x220 that doesn't even have official support for Windows 8.1 but runs just fine with an assortment of different drivers. You might have some deep digging ahead of you but most drivers will probably be provided by Microsoft out of the box.