Sure, OpenMW is awesome and all and hopefully it will breathe new life into the Morrowind Community, which admittedly it still quite active considering the game's age, but I think there is no way it will even remotely be as popular as Skyrim or other more recent Bethesda game. Have you ever compared the Activity on Morrowind Nexus to that on Skyrim Nexus? There are more than 10 times as many mods on the Skyrim Nexus page than on the Morrowind one, although the Morrowind page has been around for much longer. The top Skyrim file has over 9 Million Downloads, the top Morrowind one not even 1/4 of a Million - over almost twice the time if the numbers are correct.
But there's more. Skyrim has been sold almost 24 Million copies according to
this page, but only a quarter of them have been the PC version (as shown
here). That's still more than Morrowind sold on all platforms together, as far as I know. So only a quarter of all Skyrim players can use mods, and probably even less actually do. Considering that a significant part of the PC copies were probably sold in a relatively recent Steam Sale for a fraction of the original price and the console versions were more expensive to begin with, it is probably safe to assume that most money came from people who can't even use mods.
Given that OpenMW is clearly made for people using mods and making mods themselves, it should be safe to assume that no matter how popular it turns out to be, it will under no circumstances become a financial threat for Bethesda. Maybe it will even be the other way round... just as Skyrim possibly has brought some people to Morrowind there is a chance that in the future, people who play newer Bethesda games will find OpenMW and buy Morrowind to play it on the new engine. Maybe there are even people who are put off by how the Original Morrowind looks and feels compared to Skyrim and OpenMW will provide a more up-to-date experience for them once it has reached 1.0.
Anyway, the question was answered, anyway, so I just wanted to put your post in proportion.