Not all grounded conductors are white, and not all white conductors are grounded conductors.

There's no problem using a white or gray wire as an ungrounded conductor, as long as the conductor is permanently reidentified.

National Electrical Code 2014

Chapter 2 Wiring and Protection

Article 200 Use and Identification of Grounded Conductors

200.7 Use of Insulation of a White or Gray Color or with Three Continuous White Stripes.

(C) Circuits of 50 Volts or More. The use of insulation that is white or gray or that has three continuous white or gray stripes for other than a grounded conductor for circuits of 50 volts or more shall be permitted only as in (1) and (2).

(1) If part of a cable assembly that has the insulation permanently reidentified to indicate its use as an ungrounded conductor by marking tape, painting, or other effective means at its termination and at each location where the conductor is visible and accessible. Identification shall encircle the insulation and shall be a color other than white, gray, or green. If used for single-pole, 3-way or 4-way switch loops, the reidentified conductor with white or gray insulation or three continuous white or gray stripes shall be used only for the supply to the switch, but not as a return conductor from the switch to the outlet.

There is a problem with switching the grounded conductor, but no problem switching a white conductor (as long as it's reidentified).

Chapter 4 Equipment for General Use

Article 404 Switches

404.2 Switch Connections.

(B) Grounded Conductors. Switches or circuit breakers shall not disconnect the grounded conductor of a circuit.

Exception: A switch or circuit breaker shall be permitted to disconnect a grounded circuit conductor where all circuit conductors are disconnected simultaneously, or where the device is arranged so that the grounded conductor cannot be disconnected until all the ungrounded conductors of the circuit have been disconnected.

Before the introduction of 404.2(C), two wire switch loops were common. Since a two wire cable only has a black and white wire (and ground sometimes), the white wire had to be reidentified and used as an ungrounded conductor.

Yes. If you're not making changes, there's no requirement to swap them out. If you are changing out the receptacles for any reason, you'll have to install tamper resistant receptacles. You cannot replace the receptacles with non-tamper resistant receptacles (technically).