if you want to use TTs and scratch, then yeah, why not? if it’s just purely because of the 50% deal, then you need to give it some proprer thought imho
set-up the time code, set traktor to internal mixing mode and you can use your current midi device to control the mixer side of things and the time code to control the decks.
Just as a note - the only TSP upgrade on the offer is the one for owners of an Audio 8/4 or a certified mixer, the offer explicitly exludes hardware bassed upgrades(which is irritating as I want to go TP-TSP, but only have an AK1)
e2a: just spotted you said you had an audio 4 - d’oh!