I thought about asking this question on meta awhile back, but I figured that expat-specific questions will be considered "off topic" on this site.
Consider the top 5 on-topic questions for the Immigration proposal:
- What do I need to open a bank account in [country] and what is the best way to transfer money to it?
- Is my UK driving licence valid in [country]?
- What is a typical salary for a [trade/profession] in [country]?
- Can I work legally in Argentina without being a citizen?
- What are the legal options in order to immigrate to [country]?
I don't think a single one of those questions would be considered on-topic on the Travel SE (maybe the driving license question, depending on how it was worded).
The two sites will undoubtedly be complementary, but they will have their own exclusive domains.