I value a game based on what the developers and publishers put into both prior and post release. If the companies are known for great support of games post release that makes me want to buy the game even more. If not, I usually wait several months and see what support it will get. If I was still PC gaming I would wait about 6 months before getting NWN 2 for Obsidian and Atari have a poor history of supporting their games.
As for mods putting value on something that has a great deal of uncertainty such as is stupid. You said with "probably good content" and I prefer not to deal with probabilities, only certainties. Your analogy is false. With a DVD player I can buy more and more DVDs to add to my collection and the DVDs are done by professional manufacturers, and created by companies who strive to make a product worth buying. They have a financial risk and thusly motivated to release the best product possible. Mods are done by amateurs to support their chosen game to mod. They are not developers, not publishers, not a company with financial backing, just simple modders.
I will judge NWN 2 as I have judge Jade Empire, Knights of the Old Republic, Icewind Dale, Knights of the Old Republic 2, Neverwinter Nights 1, Fallout 1, Baldur's Gate 2, and so forth and so on. I will judge NWN 2 on its own merits as I have on all games that I have played. No more and no less.