welll... it's true that sierra is owned by vivendi, but i don't know how much that influences what games they make.
the company i work for (a publisher of patient education materials) was owned by vivendi when i started working here. you wouldn't know it, except for the fact that it said "Vivendi Universal" on our employee handbooks. vivendi was basically a silent partner -- they provided our health benefits, among other things, but didn't seem to have any say in the products we put out or the direction that the company went.
vivendi recently sold us to another company. there have been changes in our health benefits, the way our HR department runs... day-to-day internal differences, that mostly seem to stem from the fact that we aren't owned by a parent who tosses money at us anymore. but i haven't seen *any* difference in the products or the business strategy. i really don't think vivendi had any say in what kinds of products we released... just as long as we kept making money (and clearly, at some point they lost interest in us, and we were sold).
i'm not saying it's the same for sierra -- and i don't work in management, so i'm only speaking from my observations -- but i highly doubt that sierra's lack of interest in the adventure game has anything to do with vivendi. ken williams has said in interviews that he made a big mistake selling sierra initially... it was at this point that the founders lost their control of the company's direction. the company has changed hands so many times since the "good old days," now it's just a name. i don't think any of the people in that company have any interest in resurrecting sierra adventures the way they used to be, simply because the people who work at sierra now are not the same people who worked there back then. why should the current president of sierra care to support a culture that has long since died away, and has nothing to do with sierra as he knows it?
it might be easier for all of us if there wasn't any "sierra" presence, because maybe we'd stop getting our hopes up that they might do something with the copyrights they hold. but i think even if they were to do something with the franchises, it wouldn't be what we want. clearly they're making money, or they wouldn't still be around... why should they bother straying from their business model (which appears to be working for them) to please some fans who loved the company 15 years ago? what's in it for them? if some of the original sierra employees were in management, i think it would be different, because they would have an interest in maintaining the culture they developed. but as it stands, the old timers are gone, and the current management has made it pretty clear they don't want to re-initiate those old relationships.
hope this made sense, i don't feel like i'm articulating very well.