AKG wrote:

Oh, I'm just wondering if this argument would necessarily have to commit us to creatio ex nihlo, like the Kalam tries to show.

Well, if there is some way besides creatio ex nihilo to get contingent beings from a necessary being (or several necessary beings), it doesn't commit you to creatio ex nihilo. If there isn't, it does.

In this case, would this necessary being merely create contingent beings and leave them be afterwards or would it continually sustain them in existence?

Here is one way to bring out the question: if, counterpossibly, the necessary being ceased to exist after creating the contingent being B, would the contingent being continue to exist?

I'm not sure, and I'm not sure that 1's argument on its own can decide the matter either way.* (A counterpossible is contrary to possibility: we're in the realm of pegasii and square circles with the above.)

*The concern, I suppose, is that we would be smuggling in Thomist theses about existence to answer that if the necessary being ceased to exist, the contingent being would also cease to exist.