Well, if you're right, I shall be the first to petition the dons to change your name to Mystic C64!!!

All I would say to anybody contemplating 'playing the market' to try and save a few quid, do the maths, and don't forget to add in any postage costs and interest on any borrowings taken to fund it.
Seriously, work it out, and you'll find there isn't as much in it as you think.
In my own situation, I have contemplated shifting my two GT's for say, £320 max, and replacing them with two GTS's at approx £450 delivered.
So, I'd be spending another £130 now to avoid losing £120 (at C64's forecast price of £100 for a used GT in Feb 07) if I sold in Feb 07.
But, you're saying my two GTS's could be worth as much as £160 more for a pair come Feb 07, saving me a whopping £30 over hanging on to the GT's...
If you're wrong about either the price of the GT's or the GTS's in Feb 07, then the maths make even less sense.
The maths works out for one card too.
All this would make more sense if the GTS was a big step up in performance over a GT, but it's not.
Seems like a big risk to be taking around something nobody knows much about, ie future used graphics card prices.