Not quite. The point is the qubit also holds the information of all operations applied up until the point the sequence is completed. The limit on that is the ti

Not quite. The point is the qubit also holds the information of all operations applied up until the point the sequence is completed. The limit on that is the time to decoherence, not the number of qubits (although the more you have the harder it gets to stay coherent). That does mean that the result you get from the calculation can be nothing more than the classical equivalent, but the amount of inputs to that result, and the resultant enormous explosion of processing you can do on it (each operation yielding potentially exponential growth in evaluated possibilities), is dependent on other factors.