I do understand where you are coming from. I signed up for updates for the VIP Pass, as I am going to California, so could have used it at Legoland and also going to Heide Park to ride their new coaster later this year, so could have justified some of the costs of the £500 pass at these parks, especially as day entry to Legoland California works out to be about £60 !!!! (No discounts available unlike the Merlin UK)
However, havent heard anything, so now unlikely to be spending that kind of money on a Legoland park.
I did ask at the time of the annual pass sale, if I could buy a Premium pass and then upgrade and was told that no you couldnt do this. So like you, I didnt buy anything during the sale, in case the VIP pass will work out to be great value.
By the way, with regards to Unlimited fastrack, it hasnt been clarified as to what the VIP pass entails. I think that it will be just one unlimited fastrack once for each park (excluding Legoland)