While cynical me knows that the author name on the cover unfortunately isn't very important in tie-in fiction, I'd like to think that the recognition Ms. Beyer has been getting for the quality of her work is at least part of the reason why the line has been kept in her hands for now, at the cost of limiting its output to her capacity.
And I think waiting has its upsides. For example, there's a lot of grumbling from the 24th century fan camp about the TOS stuff dominating the first half of this year, but OTOH it builds up anticipation for picking up a Trek novel again and perhaps avoids over-saturation. If you know your audience is split to a degree, scheduling like this might actually make a lot of sense to keep readers around for years and years without wearing out their attention spans.
Also, what's this about the second relaunch series ending? AFAIK Ms. Beyer is hard at work on another installment.