Actually, Diane - McDonald's has already made the switch. Their fry oil was a blend of several oils ... trust me I know because my son used to blend it when he worked for (the company that makes it) ... the new oil doesn't have that same blend ... or flavor.
I got some McD fry's a couple of months ago and could not believe how bland they were since the change! (Not to infer they just changed a couple of months ago - that's just the last time tried them .... which I only do about 1-2 times a year)
"It ain't what you don't know that gets you in trouble. It's what you know for sure that just ain't so." - Mark Twain