As a Glorantha fan that doesn't play there as much any more, I think other stuff is needed and good. I will say, however, that it is my opinion that Glorantha needs to continue to be supported AND...that folk shouldn't shy away from the books simply because they are "Glorantha."
One of the things I absolutely love about the MRQ2 line is that- having bought everything except the Elric and C&C stuff- everything works together. You can litterally use all the books together and have an almost endless supply of adventure hooks and so on.
Between the Vikings book and the Glorantha book- and the Wraith Recon book- I can't imagine running out of ideas for at least four years, letting with a group weekly. Seriously. There are that many.
That said, I already know that the Elric stuff and C&C stuff have great stuff I can use in them, and I may well get 'em eventually- for simply that reason. Especially C&C if I want to get into black powder stuff (they seem to have really figured that stuff out well from what I've seen in S&P. Great job guys).
So, for me right now, it's more monsters (Monster Island), more spirit and gristly magic stuff (dark S&S stuff- Blood Magic), and maybe a Greek or Roman book like the Vikings book (I would seriously consider a Vikings vs. campaign if this happened. Awesome).
I will add for Matt though, that I, for one, realize a lot of stuff has been released for MRQ2. We all just love it so much, we want to see more.
Let's say, just for argument's sake, you're right...