We generally do not get advance notice of park ticket increases. IIRC, the price for annual passes was last increased in January, 2005.
If you have the $$, it wouldn't hurt to order the voucher(s) now to lock in the price. If you order via phone or online, your year of admission will not start until you exchange the voucher for the actual pass. You must do the exchange on site at WDW.
To get the DVC discounted pass, you'll need to either order online via the DVC Members' website or call MS.