Mixed emotions mate, sorry to see you sell up but pleased for you that you will get to own another great car, and it will be good to get a good look at one.
As you say you might come back to it, with the GTR still likely to keep depreciating a fair bit, if it was me i'd have a shot of one for a few years and sell it to recoup most of the money back. Thats something gladly you dont need to worry about too much with a supra, as they tend to hold their value quite well.
Personally Owning a MKiii and then a MKIV supra was a life long dream that i was lucky to fulfill and i really feel like i will keep it until it gives up. I wasn't too interested in modding it when i first got it but because of this forum and the people on it that are so helpful and good natured that opinion has changed and now see the light with regards to BPU. It really is a great forum because help is always at hand, and that comes from guys who have sold up too.
As has been said a few times already, i've also had the car away this winter and last and it gives you a buzz to drive it again after being away from it for a bit