Prospecting pets in bfa

[Tekulve2018]

I wasn't sure what forum to post this question in..but it's been on my mind for a while and I can't find feedback anywhere else.
Preamble:
I enjoy collecting, buying and selling pets on a few realms. The WoW auction houses vary greatly due to realm pop.
All that being said, I have seen other expacs drop and new pets often cost a fortune in the early days.
Reputation pets start with nutso prices then calm down after their availability grows.

Many people vow that they wont buy expensive pets early on..I get that, I have limits too.
I also know that there may be new raid drop pets that have not been announced or available Aug 14th-
raid drop pets tend to hold value long term.

Question:
For those who have played Beta and/or who have researched this question, what BfA battle pets are likely
to retain solid value because of difficulty to attain and/or expected low drop rate?

I understand that answers are speculation. .that's all good, thanks.
Tekulve