I'd say we don't need any pointless ships, that don't actually add anything new to the game. Hopefully any new ships can do something existing ships either cannot do, or can't do as well (but without eclipsing existing ships... which is difficult to manage).
For instance, what we know about the Mamba is that it's a bit bigger than a Python (but probably still medium), with apparently oversized engines, and was a "racer" in lore. We don't know how that translates into ED, and whether "big engines" only refers to thrusters rather than FSD. If it's merely fast in normal space, it might be a medium-sized rival to the Courier and Clipper. But if it has a size 6 FSD in a medium ship that weighs about as much as a Python... then it will out-jump the Anaconda.
And why shouldn't it? Why not have a stripped-down "racer" ship that is mostly engine outjump a bulky freighter? It would be something new, and it certainly wouldn't replace the Anaconda.
Or perhaps the Krait Phantom will do that. We know it's smaller than the exiting Krait, preumably it's lighter, but we don't know what size FSD it will have. If it's downsized to a 4, jumprange is likely to be disappointing. But if it stays at 5, in a lighter ship... that could be useful. Not sure what would happen to the AspX in that case. Possibly if it requires Guardian tech, it could replace the AspX for those that do the Guardian grind.