Just upgrade. There is really no point in delaying it imo. I believe you can root without tripping knox, but you have to browse the forum a bit, i've seen threads about it.
Samsung Galaxy S 4 I9505 | WanamLite v3.0
Samsung Galaxy S II I9100 : AOKP 4.2.1
HTC Touch Pro2 | ROM: Valkyrie 6.5.23115TR2.5
HTC HD2 | DarkStone1337 [FroyoStone Sense - V3.2]
HTC Desire : Oxygen v2.1.3