If a magic wand were waved such that all conservatives disappeared (say, were 'raptured') you'd simply have a new Right (former moderates) and a new Middle (former liberals) and a new left (former extreme liberals).

You wouldn't have one monolithic ideology, because the parties, despite their press and platforms, do not represent a coherent ideology, any more than loose terms like Conservative or Liberal do. They represent emergent stable points of best-fit consensus on either side of a defining line, which itself is defined by how large and powerful the sides are.