I have just a handful of the cards from 1989. I bought a booster pack that said 1989 and they were of course 1990 trademark on the back.
Your best bet is if you see loose cards just email the seller and ask what the trademark date on the back is. Some sellers list them as 1989 too and most would do so because of the date on the back and not because of the rarity.
Here are the details from a good site.
WrestlingTradingCards.com - 1989 WWF Classic
The only card from the set that I think could have some potential is the Ultimate Warrior as you could make the argument it is his rookie card. Personally I like the Market Scene card more and would like to add one to my collection at some point.
There is no chance in my opinion that this set takes off in price as they are essentially the same photos as the 1990 set and there are 10 sets for every person who could ever want one of those.