Maybe.
SR should either work like 3e DR, or like 3e Evasion.
That is, maybe SR only applies to some spells (SR 5/necromancy, or whatever), and reduces the effectiveness of those spells without necessarily just negating them.
Or, alternately, SR works like evasion, in that whereas a normal character takes half damage on a successful save, the creature with SR instead takes no damage. Again, I'd be inclined to limit this to specific types of spells only.
What about for spells like hold, charm and the like, that don't deal damage?
So werewolves will have Resistance to Non-Silvered Damage while Ghosts may even have Immunity to non-magic Damage.
My money says ghosts will have resistance not immunity. Magic items will be much rarer in the new edition as a base and I they will likely keep the points of later editions with allowing everyone to participate. Outright immunities will probably be very rare.
Well, but "you can only kill a ghost on the second Tuesday of the month while changint the world Eulalie OR with a +2 or better magic weapon" doesn't really sound like a decent mechanic.True, but Ghosts have always been the poster child monster for 'you can only kill it on the second Tuesday of the month while chanting the world Eulalie'.
Spectres, Wraiths and Scaryhead Fadingdeads will probably all just have Resistence though.