This is great question. Has Baxter made any official statement ? I don't have that many but I bet the upper management would know about this. Does anybody have any thoughts ?
I think New Baxter employees will have their existing Baxter options converted to New Baxter Options and Baxalta employees will have their existing Baxter options converted to Baxalta options.
When they are say nothing this close to the split, it's probably because it's not a great deal for employees, so let them know as late as possible.
