Section 1
Successorship:
"The provisions of this agreement shall be binding upon any successor or merged company or companies unless or until changed in accordance with the provisions of the railway labor act, as amended."

So the company would get the union in full legal capacity and have to bargain with ALPA.

Allegiant most junior CA: Nov 2007
Spirit most junior CA: May 2007 and getting younger

Allegiant started in 1997
Spirit started in early 1980's as charter, most senior person on list is 1990.

I don't know the work rules of Allegiant, but Spirit has some pretty good ones (my opinion). In any case, the pilots would hopefully negotiate up to the better provisions of either set, and have appropriate fences for a set time. It would be interesting, for sure.