If a circuit breaks contract, they suffer massive financial penalties, ask Brands Hatch. So even if Ecclestone goes, which I don't think he'll do until he's dead and buried, then there's no way past the contracts in place for the reasons I have mentioned.
Finally, the GPWC didn't get far. It's all been tried before. And we're still watching Bernie's show.
I haven't read the contracts, but I would suggest that they're not the immutable end-all-be-all force one might think. When the structure of one party in an agreement changes, it can have ramifications.
... and as evidence of the whole fluidity of things at that level, as you point out - we're watching Bernie's show. Bernie has been the glue of the business side of F1, which is why such a consortium could not have happened before. And in turn, the vacuum that will be created when he's not there will alter things: it will no longer be "Bernie's show", and the label "F1" as a brand could be argued to be lessened or completely restructured as a result.
I would not be surprised at all - I expect - that many of the agreements scattered about the F1 frontier has Bernie's name and associated legal entities interwoven in many a seemingly innocuous way. I think people are going to be in for a fright. Maybe not, but we'll see, right?