Also, keep in mind Sunday is a "school night". People flying in for a Monday morning meeting will typically arrive on Sunday. I am a Diamond with MyWay Preference for points across the board. Many times I also get an upgrade, but it's never a sure thing. If your stay is just one night, then there is a chance. Go in expecting what you booked and enjoy anything better than that.

Also, even if you don't get upgraded to the Executive Floor, ask about lounge access, they may be feeling very gracious and grant it even though not required.