Plumeria recovery

My 12-15 year old plumeria got a bad case of frost bite this winter. It has not come back yet and the branchs are getting spongy. Is there anything that can be done to revive it, or is it gone forever?

It probably has root rot. I would do multiple things:
[1] without over or under watering, treat the soil to significant depth with Spectracide \"Immunox\".
[2] try to locate some branch ends that are more firm than spongy. cut a few of these off, wet the bottom two inches, coat with Root-tone and immediately plant in a prepared 12 gallon pot containing plumeria mix or a citrus/palm planting mix. Before planting, wet down the soil in the pot and use something like a broom stick to make a four-inch hole to receive the cut stem. The goal is to place the Root-tone coated stem in the hole without disturbing the root-tone, then press the soil in the pot up against the cutting. Place in full sun. Water 2 to 3 times per week. The soil should never be dry at the bottom of the pot (check the holes at the bottom), but also should never be soggy.