The pilots have been offered 13.5% of the "NEW" AMR. That alone should tell you the stock will be cancelled.
I see no situation where the old stock of a bankrupt company is NOT cancelled. If anyone knows of one I'd be interested in reading about it. I don't think it hasn't happened in the airline industry.
Also, technically, the deal hasn't yet been signed. Yesterday the tentative agreement was only passed by the membership. There are some housekeeping issues to take care of before the deal is actually signed. Under these circumstances I would guess this will be done sooner rather than later.
One reason they can do this quickly is because AMR has a horrible track record when converting a T/A into contract language. Things they didn't get at the negotiating table they take when they actually write the contract and tell labor if they don't like they can grieve it or sue, knowing it would take years to litigate. One of the big reasons the last T/A was voted down was it was not in contract language. So the pilots insisted on contract language. This one is already mostly done, so AMR cannot abuse the situation.
And people wonder why there is so much friction between pilots and AMR.