So, I'm think it is time to replace my HV20. (Well, I have had a couple cameras in between)

I see the new G40/XA30 is announced and doesn't have 4K.

So, I'm thinking the way to go is a -used- G30. They seem to go for $900. I'd much rather go for this technology level at that price point.

My primary use will be shooting burlesque shows. So questionable lighting is the norm. Is this still considered the best camera for this kind of thing?

Was thinking of a Panasonic Lumix DMC-G7 but I need to be able to do clips over 30 min. I failed to win the powerball so Sony A7S2 is out of the question!

Does this plan make sense? Or is there some other camera I should be looking at?

If low light is of high importance, the HF G40 literature claims significantly improved performance over the G30.
But it is not due out for few weeks and will probably command "full price" for a while longer.

Used camcorder may come without warranty depending on where and how you buy it.

Correct, I don't want to pay $400 for that upgrade--I could probably get a GH4 for that. I'm guessing it would be better at low light than the G30.

I'd like to buy it from a store and get a 30 day warranty. I got some more time to think! The two that I saw were sold!

You might want to think about a Panasonic HC-WXF991K

Just checked out the current Panasonic offerings. The G30 has a nice heft to it. Panny seems really flimsy to me.