One issue: Neither of those games were ever advertised as having mod support. Neither had modding communities.
Saying that modding was never a priority for them is totally fair. But do you really think that after all that happened with Aliens: Colonial Marines, they would actively and knowingly lie to their customers again?
Actually, you are wrong. At least DNF was promised to have mod support, but it's probably bit more convoluted, as the promise seems to originate from 3DRealms and not from Gearbox. You are also mistaken in the belief that DNF wouldn't have modding community. The reason it does not exist is solely Gearbox, they have done everything to make the game unmoddable - even more so with updates
. This has more to do with Gearbox selling downloadable content later on, and I really don't see why they wouldn't keep on going that way. Please note that the site is actually a modding community for Duke Nukem 3D, and these guys would be happy to work with anything more modern than Build engine. A lot of people were furious about DNF not having the tools, they really wanted to fix the darn game themselves, but no such luck. The same thing with A:CM.
Also, a lot of people thought they give Gearbox a second chance with A:CM after DNF was released. So in my opinion, Gearbox has already been given the second chance where they knowing lied to their customers.
I don't know what to make of this, though. Since Gearbox is already in legal trouble over A:CM, for me them acquiring Homeworld rights sort of sounds like an intermediate source of cash. Nothing wrong in that in itself, but given the recent history, I'm very skeptical about the outcome. Of the original announcement, I don't actually see where the modding support has been promised by the Gearbox. They have released a survey, but that's not the same as commitment. In their forums, one of their developer says some of the tools have been developed, but again, whether those tools are included in the release is another thing.
The company's history shows they want to sell DLC instead. At least I'd actually wait for the reviews before giving any money to them.