I have to respectfully disagree.
Disney tends to want Blizzard Beach open during Christmastime
as it is already decorated for the holiday (all the time.)
But, if necessary, they will swap which WP will be open,
and which will be closed during Christmastime.
(No way to predict, before they announce.)
Figure that one WP will close from near the end of October,
through the early part of January...
at which time that first-closed WP will reopen,
just as the other WP will close...
through the middle (or later) of March.
At that time, both WP's will be back open
through the rest of the warm season...
until late October begins the refurb cycle again.