As of the Playtest Packet from September last year, no.
The proficiency bonus is only mentioned as a Spellcasting Bonus under 'Magic Ability' for Bards, Clerics, Druids, and Mages. Paladins and Rangers, (who only get access to spells later in their career), do not have it added on.
This is also specified in the 'Magic' section of the 'How To Play' document:
Many spells specify that a target can make a saving throw to avoid
some or all of a spell’s effects. The spell specifies the ability
that the target uses for the save and what happens on a success or
failure. The DC to resist one of your spells equals 10 + your magic
ability modifier. If you have a spellcasting bonus from your class or
another source, add the bonus to the DC.
(If someone has an updated version of the packet that corrects this, please mention it - it seems WoC took the packets down last year so I can't find a copy beyond what I used last year).