Dell firmware updates and newer Ubuntu versions

Dell firmware updates, if I am not wrong, are located in the restricted repository.

If you manually install Ubuntu 17.04, just type in a terminal sudo add-apt-repository restricted. Then, search for Dell firmware updates in GNOME Software center. It will work like Ubuntu 16.04, where you still receive firmware updates, unless Dell really decided to abandon Ubuntu's firmware updates (which in this case, Ubuntu 16.04 will also be affected.)

But the best choice, of course, is to keep your existing Ubuntu 16.04, install 17.04 alongside, so that even if you encounter problems, you can still fallback to 16.04 and ask something here.