If I go from 9-42's to 9-46 Hybrids will I still have to adjust the truss rod or is this such a small step up in guages that I shouldn't have to worry about it ?
Any change in ANYTHING having to do with strings (if you want it PERFECT) would require a truss adj.
However, sometimes the change is almost imperceivable to the eye. The type of string gauge change you're anticipating is so slight your eye will barely pick up the resulting bow.
I've gone from EB 9's to 9.5's (another brand) to EB Hybrids on one of my Silos, and it never needed an adjustment. The little extra tension from the heavier strings seem to have been made up for by the additional string thickness. Anyway, truss adjustments on a MM are a snap, in case it did need a tweak.