I like the Tiguan also and it's a good deal right now but that's mainly due to it being well past its due date. It's based off the MK5 Golf platform, which is two generations older than your Golf R. Have you factored in the extra maintenance cost of the Tiguan and the cost for supreme gasoline.
How long until the F150 is paid for? How many Kms does she use in a year? Like you said, the truck has retained its value well and waiting till it's paid off would put you in the best possible financial position. I would think the only reason to get the new vehicle is because you can not afford it anymore.