I sincerely doubt it. McCain is much closer in political outlook with the senators you named than Bush. Why would they support Obama unless out of office? They risk losing all support if McCain wins. They have nothing to gain by supporting Obama. I can see why you might believe someone like Snowe would switch, but Orrin Hatch? Please.
I suspect it has more to do with Bush than with McCain or Obama. Jumping to Obama is a delayed reaction to the current administration. Under other circumstances these people would be more than happy with McCain.
And no Republican in Congress is going to endorse Obama unless he or she plans on changing parties and crossing the aisle. It's easier for those who hold no office to do things like this.
I believe that Orrin G. Hatch has long had a personal rivalry with his AZ neighbor McPain.