There are a lot of podcasts out there, so it helps to know the source. While I can't rule out the accuracy of the report, there's been no official word from DCL yet, and probably won't be for a while. Meantime, it's safe to say that there will be six-passenger staterooms, if for no other reason that the current ships also have a couple of six-passenger suites.
The real trick with six-passenger staterooms is the price charged for the space. With shipboard square footage being at such a premium, you can bet they won't build anything that would give them a lower-than-average return on that square footage. Judging by the rates currently charged for Cat. 4 Family Suites (sleep 5, rather than six), a six-passenger family suite won't be cheap.
If they build family suite-style staterooms with the equivalent square footage as two current Cat. 8/9 or 5/6 staterooms, it's highly probable that they'll charge enough to get at least the equivalent of the fare paid by a family of six occupying two staterooms - 4 full adult fares and 2 additional guest fares. On the rate chart, it may look like they're charging for two adults and four kids, but the basic rate for the room will be higher than the cost of two adjoining rooms, to compensate for the lost revenue.
Another possibility would be to have a family stateroom 50% larger than a single stateroom that would hold a family of six (let's say, with four bunk beds and a queen). The charge for that space could be lower than that for two adjoining rooms, but still higher on average than the rate they'd charge if the space was used more conventionally. Two such family suites could be fit into the space of three regular staterooms. In that case, they could charge the equivalent of three regular adult fares and three additional passenger fares for a family of six, which would be a savings for the family but no economic loss at all to the cruise line.
Chances are, no matter how many of these family suites DCL decides to build, they'll err on the side of caution. As a result, low supply will drive the demand-driven rates for those rooms higher than that of more conventional stateroom space.
But it's all speculation at this point.
