Do you think it will be worth it to purchase the PC version solely for the eventual mods that will become available? If you were to ignore the technical advantages (like no framerate stutters and the option of 1080p) and didn't really care for the additional bosses, weapons etc, would you buy it solely for the modding potential?
"And that's why you run AWAY from the protoplasmic abomination trying to ensnare you in the caustic dissolution of its own cells". - Andy Waltfeld
If you're going to buy it solely for potential modding, then wait until that's realized. With no official mod support, it will likely be a while before a modding community develops (if it does at all). The game may have fallen in price by then.
It depends on how good the mod content is, if there will even be any.
I don't think it would be worth it to buy it just for the mods though (the game and extra content should be good enough for that), as it'd unlikely receive the support something like TES or TF2 would receive. Who knows though, maybe it'll be a surprise hit with the modding community.