Hello, Volt main here.
Gauss isn't going to replace Volt. If you play Volt purely because his speed and see Gauss as a threat because of it, you aren't using Volt correctly. Volt is damage (Shock and Discharge), CC (Shock, but mostly Discharge), defensive (Electric Shields), and support/utility (Speed and Capacitance augment) in one frame. EDIT: Volt also has a ton of use against Eidolons because of his shields.
Gauss, on the other hand, seems like a purely (or at least mostly) offensive frame with buffs only to himself. Mach Rush is just a free K-Drive that knocks people over (further proving how useless K-Drives are ***W H E E Z E***) with smashing your face into walls having a benefit other than comedically breaking your nuts on a lightpole. Kinetic Plating would be replacable with Adaptation if it didn't return Energy to him. Thermal Sunder will probably take too long to set up and/or would kill enemies before the Blast overlap could be used, and Redline is like Volt's "go fast" button with some added benefits to Gauss (that doesn't affect his teammates) like added firerate and the kinetic bolts it fires out, but then again Shock Trooper exists (though to be fair, I wouldn't use it over Capacitance).
All in all, from what I can tell Gauss is for the Volt player that likes flying solo, or for some reason hates archwing transportation in PoE/Vallis. Gauss has a niche, Volt is a Jack of all Trades.