This is an expression for talking about time loosely. "The next week or so" means "about the next week". It could be in 5 days, in 10 days, etc.
I'll be travelling for the next week or so.
Other phrases that use "or so" include:
- the first day or so
- the last year or so
- for an hour or so
This is one of the best songs I think I've heard in the last decade or so.