Yes, it will fill in. I have 3 pear trees. Two are solos (orient and bartlett) and the third is a 6 in 1. Two of the bud grafts didn't make it. I've seen this too on some various plants. They say it's not curable, however I'm emailing GreenCure.net about the affects of their product on the subject and should get an answer soon. GreenCure, I use on my Fruit trees to cure the black spot and premature yellowing leaves and it's safe for my honey bees too.

Here's what I would do: Once identified, remove that portion and BURN. Gather ANY leaves on the ground related to fire blight and burn them too. This is a bacteria that only affects fruiting pears and certain apples. The leaves turning red are fine. This is a weird year for fruit tree issues all together. Some of my peach trees leaves turn orange/yellow and stay that way until fall. You could try something the next time you see the fire blight. Rather than remove the limb, remove just the leaves on the stem and dispose. Later on watch the bark on the newly leafless stem for signs of canker. The bark will go from the usual green/brown/yellow color to black. Then cut it off, otherwise the limb might grow new leaves.

Here is a link that might be useful: Green Anything !