Depends solely on the carrier (FedEx, UPS, etc). It is possible it may not come until 8pm. If your packages normally come around noon, you'll almost certainly be fine though.
I'm not sure how it works with a work address unfortunately, but if it's UPS you can sign up for a MyUPS account and then you get a much more accurate delivery window. The reason this may not work for a business is that typically the MyUPS account works by tying the account to an address (so if a package is on its way to you, you get notified -- obviously you don't want to get notified anytime any package gets delivered to your work!). I'm not seeing the same thing on FedEx. The only thing you could do if it was FedEx is use their delivery manager and pay $10 to have it show up in a 2 hour window of your choice. Looking at my order, it's too late to do that at this point sadly, so you'll probably just need to roll the dice and hope for the best. You'll very likely be fine though since you said it normally comes at noon.