Yes, it will grow back.
I do not have a coated GSD, but I have a coated mix similar to a GSD. We adopted him when he was 1.5 yrs and he came with the "lion cut" (back end, legs, and tail SHAVED) because his previous owners neglected grooming. He looked ridiculous for so long, but it all grew back.
I have developed my own ways of grooming him because the groomers just want to shave him or cut it all off.
Ears - I trim along the edges to "shape" the ear (note: my dog has floppy ears). Then I use the thinning shears to shorten the hair on and around the ears. I brush REALLY well behind the ears (gets matted there) and sometimes just trim that hair really short. There is so much you cannot tell if I cut a lot out right behind the ears.
Breast - If left alone, he gets a lion's mane, lol! I just use thinning shears until I like the length. He gets a tad bit of a "skirt" towards the lower part of his chest/breast so I may trim that off with a regular scissor and then use thinning shears to blend.
Front legs - He gets LONG feathering on his legs. I like a little bit of it (don't want it shaved right to his leg), so I trim it with a scissor and then use thinning shears to blend/thin out.
Privates (underside) - If I had a shaver, this is the part I would shave. But I don't, so to keep him cool and avoid mats, I roll him on his back and basically hack off all hair from his penis on back. Luckily he is neutered, so I don't have to worry about bumping/cutting anything else! The hair back here is so long, it gets matted and he hates being brushed here. It's easier and cooler to chop it off, and you cannot see it.
"Pants" - the fluff on the butt and the rear legs I call the "Pants". I kind of like the pants, but not when they are out of control! I generally cut off a lot of pants on the inside (around the privates and inner thigh). Then lightly trim the remaining pants and use thinning shears to trim without a "hacked" look.
Tail - Like the pants, I like a fuller tail. I trim it a bit to remove split ends and use the thinning shears to blend the trimming and that's it.
Oh, also, I do somewhat of a "sanitary cut" where I cut the hair around the anus and the underside of the tail near the base VERY short, then just sort of blend the length with thinning shears so it tapers off.
I actually like doing the grooming, it's kind of fun and I can make him look how I want. All I have are a regular hair scissor, thinning shears, rake brush, and pin brush.
Coke when we got him:
Coke fully grown out, yikes!
Coke trimmed (currently trimmed down even a little shorter for the summer, but no pics):