Historically speaking, did the forums get a lot less active when Oblivion was released, and then activity increased as the new release became less new? My hope is that, perhaps as Skyrim loses some of its new-game shine people will get bored of it and start coming back to the Morrowind forums, and be here until the next TES is released.
Before Oblivion was released there wasn't many places for TES fans to hang out other than Morrowind forums, many of whom had been finished with Morrowind long before Oblivion and were passing time until the new game was launched. A lot of Morrowind fans bought Oblivion in the hope it would be better ,but for me i found going from a heavily modded morrowind to a vanilla Oblivion was too much of a backward leap and never took to it and it wasn't long before other disappointed morrowind fans also started trickling back.
i think people that are naturally predisposed towards playing classical RPG's will always be drawn to Morrowind if only because there are no alternatives, Thanks to the mods , Morrowind is steadily getting bigger and better and will be extremely difficult for rival game to match the depth and diversity a modded Morrowind can offer. Even theTolkein and Dungeons and Dragons franchises have so far failed to spawn a worthy contender.
If we want more people to play the game then it is up to us too make the game more attractive to gamers, similarly if we want more people to visit the forums it is up to us to make the forums interesting perhaps by making an effort to think up plenty of fresh , interesting , amusing ,intelligent topics. It is no good sitting about rehashing the same few topics over and over , year after year, we have to make an effort else it isn't going to happen.