Microsoft is upgrading systems in waves. You just have to be patient for the Upgrade. I had to wait like 2 weeks to get my computer upgraded. Eventhough, you are getting this notification from Microsoft like pretty much all computers make sure that your computer is on the list of Dell Computers that Dell is supporting with Windows 10 at the link below. Even if your computer is not on the list this doesn't mean Windows 10 will not work on the computer and load all the drivers needed for your computer. If it isn't on the list of Dell Supported Windows 10 computers there will be no drivers created by Dell.
Dell Supported Windows 10 Systems
u dont have to wait. done it myself, by going to this page. there are videos in the operating system forums and maybe here about how to do it today. i dont it myself a cpl days after it came out.