Id like a dealers perspective on what I'm about to say, but surely this facelift is actually coming at the wrong time for SEAT.
The used market is full of almost new (less than 1000 miles) Leons, and their prices are already shrinking rapidly. I paid £14,000 for mine which was £5,000 off what it was new - mine had 2,500 miles on though, but quite a few extras. Nowadays, and from the same dealer, I can get pretty much the same deal, but with less miles, for £11,000. Surely the release of the facelift, whenever it happens, is only going to harm these residuals even further.
I remember reading last year that Mitsubish refused to allow dealers to order the facelifted Shogun, until they had sold their allocation of the non-facelifted version, thus attempting to retain residual prices. I wonder if SEAT will consider doing likewise.