The voice on "Please Stand Clear of the Doors" is the voice of the late Jack F. Wagner (not to be confused with the Soap actor), who provided the voice for numerous Disney attractions through the years. Up until fairly recently, the "Welcome aboard Disney's highway in the sky" voice was the same, but recently (early November, as near as I can tell), the voice changed to a different voice.
I did notice that the voice change came when Disney added the message about
MVMCP, and Stitch's Great Escape. I don't know if they're going to change back to the old spiel after the holiday season.
Wagner's voice can still be heard at Orlando International Airport, where he provides the voice on the automated trains serving gates 1-29, 30-59 and 60-99. (100-129 is voiced by his son)
IMDB entry for Jack Wagner:
http://www.imdb.com/name/nm0905938/...IwfGxtPTIwMHxodG1sPTF8bm09MQ__;fc=4;ft=5;fm=1