Basically what the OP says: Could Congress subpoena Steve Bannon again and, assuming he still doesn’t feel like talking, ring him up on charges of Contempt of Congress again? Could this go on forever?
Of course he could be subpoenad again. And if he refused he could be tried for contempt again, It is a new infraction so that is not double jeopardy.
In “normal” times, the deal would be Congress would wait until all the legal stuff is cleared up. (I.e., went thru any appeals if needed.) Then they would subpoena again. The witness would therefore know for sure that they have to testify and all that happens.
However, if the other person’s strategy is just to stall things until there’s a GOP president or House, etc. or just plain never testify despite what the courts say, then don’t bother waiting. Just go for it.
Why? Congress’s subpoena power is well-established. It’s independent of the courts. They could issue a new subpoena tomorrow.