To throw one more anecdote on here:
About 5 years ago I raced a half and then a 10k two weeks apart. Training was focused on the half, the 10k was completely an afterthought and only decided to run it after finishing the half. They were both on rolling terrain, but similar enough. I ran 1:23:57 and 37:42.
I'm stronger at longer races (have very poor leg speed), so that biases me towards being better in the half. I'd agree that 1:25-1:26 is a reasonable goal given your 10k time despite possibly lacking some endurance.