Not that I think in a million years this would happen, BUT if it or anything like it did, your contract would not protect you. XJET is in such poor financial shape, that any buyout (and it would be a buyout, not a merger) would be preceeded by the requirement that XJET declare bankruptcy. Included in the BK filing would be that the pilots contract would be abbrogated. Therefore, no protections. In the case of an RJET purchase, ALPA would not be in a position to help much because the Teamsters (RJET union) does not recognize the ALPA merger and integration policy. The saving grace is that RJET's CEO has repeatedly said that he is out of the 50 seat business. The chance of the OP's ideas coming true are slim to none.
I do have a feeling though (and a mole in FC's office or i guess the interim cfo now....you get the picture), that BK is in the works for XJET. The contract signed with CAL is in no way profitable without MAJOR cost cutting. Most likely only obtained thru BK. Unfortunately, the industry leading contract that XJET has will be destroyed. Take a look at Mesa's current contract. That will be what mgt will be shooting for.