Wait for More Information
If you're interested in the next-generation Galaxy Note, you might want to wait a few more months before making a decision to buy or wait.
Right now, we know virtually nothing about Samsung's plans for the Note series. The Note 10 is still extremely fresh so it'll dominate the headlines for a few months at least.
That said, if Samsung is planning to launch new Note models in 2020, we should start hearing about them in early 2020 as development ramps up.
As Galaxy Note 11 rumors pickup speed and become more credible, you'll be able to make an informed decision about waiting.
If you aren't thrilled with the devices on shelves right now, and you aren't in desperate need of a new smartphone, there's no reason to force something.
Hang around until 2020 and get a better read on the next version of the Galaxy S and the next version of the Galaxy Note.