Ah, so Homeworld failed because its fans don't like the same things you do. Please.
Homeworld died because of two things:
1- Difficulty of modding, leading to small mod teams and mountains of work, leading to people abandoning mods halfway through (which happened to pretty much all the big mods around 2006). By the time it became easier, most people had moved on. Contrast Freespace 2, which was/is much easier to work with, and has a thriving mod community as a result.
2- The Homeworld license sat in Sierra's possession for a long time. Relic made DoW in 2004, and it was much more popular than Homeworld was. Why would THQ go through the expense of buying Homeworld from Sierra when Relic now had a perfectly good franschise that sold more? Chances are that THQ bought Homeworld for dirt cheap in 2008, but even then, Relic's time and funding is much better spent on a new DoW or CoH game, since they're almost guaranteed to sell more. Why bother making Homeworld 3?
Making HW3 an MMO wouldn't solve this. Dark Millennium was supposed to be an MMO, but they didn't think it would be successful enough to warrant the financial investment, so it's going SP (which actually makes me interested in it). If THQ has doubts that a 40k MMO would be successful, what chances to you think a less popular franchise like Homeworld would have?
Would you rather play a game such as HW or would you rather play EvE Online which is basically HW set in a much larger and more diverse storyline setting. I don't play EVE, but I still play HW from time to time. What do you think?