IMHO, WCW Main Event autos will never mean all that much (to the extent they even exist) because they are unfortunately just base cards signed the same as if you had a guy sign them at a show today. There would be no way to authenticate them as originals from the manufacturer short of pulling them from the pack yourself. At only one per case or so, it would hardly be worth breaking the product searching for them, albeit I don't know exactly where all that wax went (it was another item that sat on the shelf in retail stores and ended up being heavily discounted IIRC).
As for the European cards, I'm not so sure they will be the next big thing. Aside from not being sold in the US, there's really no reason to know whether these cards were in anyway limited (and given the WCW cards at least were produced by a major company like Topps I'd have my doubts). If there's even say 5,000 of each in existence are there even 5,000 Scott Hall fans willing to pay a hefty price tag for a Scott Hall "rookie" card? Currently you can buy as many of the Heyman's as you want on Ebay for a $1.50 by the way. Also quite a few of these cards seem to be mislabeled with wrong wrestlers pictured. Looks like a poorly produced product.