Bluebirds ?

We have had a nearly 30 degree drop in temps here the last few days so it was kind of disappointing not to be able to go outside without freezing today . So sitting on my couch reading today I noticed something at the birdhouse in my front yard . Could it be ... was it ... yes... no ...maybe...yes ...YES it was ! A pair of bluebirds . I was so excited . I have always longed to have a nesting pair of blues . They hung around for a while then flew away . Now I'm waiting for them to come back . I don't want to be dissapointed  They will come back ! I know it ! Won't they ? Do you think ? ...Do ya ? !