I'm guessing for this first round (beta 1). After that, I suspect we'll be back on a once per week cycle.
Always pays to look out and see when Apple might be having a product event, as major point releases frequently coincide with those. The money seems to be on an event sometime in March (prob mid to late) for a possible SE2, new iPads Pro, a possible 14" MBP etc...
Then work back from there to now to see how many betas they can squeeze in. Since we're in mid Feb and on Beta 1, going to weekly will give them up to 6 betas and a "GM" (Forum: don't @ me; I know "there's no such thing as a GM for a point releases" - hence the quotes) prior to the last week in March.