Weighing in with this Yank's point of view: I would definitely not say "talk to you soon" or "see you soon" unless there was a definite plan for a conversation or meeting in the near future. In the latter case I might also say "Talk to you in a little while" or, as my old boss used to say, "See you in a minute." (Yes, even when he meant "at the annual meeting six months from now.")
However, I also only use "talk to you later" with people I actually talk to on a regular basis---a neighbor, my mom, my husband.
I guess the bottom line for me is that "soon" has a specific appointment time attached, but "later" doesn't. Also "soon" is a bit more formal. Even if I planned on meeting my husband downtown for a drink after work, when I talked to him at ten a.m. I would say, "Okay, honey, see you later," not "I'll see you soon."
"I hope to see you soon" or "I hope to talk with you soon" implies the strong desire for an actual meeting (whether or not that desire is sincere). Very useful for ending a letter.
"Dear Auntie Mary, thank you for the wonderful sweater. It means so much to me to know that you knitted it yourself and really, if I tug hard on the left sleeve it looks almost the same length as the right one. Hope to see you soon."
"I want to thank you again for the job interview, Mr. Potential Employer, and I hope to hear from you soon."
Just my viewpoint
[native speaker & writer, not a teacher]