Based on what've read so far, the F10 M5 should be one helluva car (despite my dislike for the F10 in general). If I were you, I would wait to test drive the M5 before putting money down for the Panamera.
By the way, the M5 will not have a spare either if it continues the M tradition. You'll end up with an M-Mobility kit.
BMW CCA Member #xx4477
2006 Z4 M Coupe (e86) 6MT
2013 M3 Coupe (e92) 6MT