It's current valuation is based on an assumption that the revenues will continue to grow significantly.

If it turns out that in reality the revenues will be stable/stagnant, then the owners of Apple are in for a rude shock (since it'd mean that Apple is worth much, much less), would not consider this situation as acceptable, and would be ready to install new management and approve radical changes to try and continue growth (of both revenues and share value) by any means possible.