I don't think crew-change by boat is going to be bad news for the helicopter companies. The limitations in terms of sea state (for basket transfer or similar) are very restrictive and that coupled with a 10h+ journey to and from the rig is not going to be a sustainable long term solution. However I'm sure it will provide welcome relief in the short term (at least for workers stuck offshore).
The real question is going to be over who picks up that tab for consequential losses due to the unavailability of the aircraft? My guess is that Eurocopter will have some liability however I can't see them paying for lost revenues because oil companies can't get their staff to and from the rigs ...