I think he'll make . 是表达说者的各人意见/预感 这里 make 是 当作 的意思
promising means judging by his other book that I've read, I believe he's showing great potential and I dare say he may have a bright future as a writer/become a great writer.
跟：He seems to me a talented young writer of great potential. 意思一样 = 看来他很有才/是一个很有前途的作家,潜力很大的才子