Clarification: The limited timeframe was about 14 months if I take a look at the announcement, you may also choose then to keep your Classic toons… For free if you opted only for one version at that time. Choosing both did require a paid version.
Edit: No toons were deleted but only progressed with the realms when they were updated to match the expansion then as otherwise claimed, the toons were found to be at the destination Wrath realm as expected.