The new ships are supposed to be around 158,000 tons and hold 4,100 passengers. We sailed on the 160,000 ton Freedom of the Seas which "only" holds 3,600 passengers, and we felt crowded! I don't think this will be our class of cruise ship.
No Mexican Riviera cruises are on the horizon for us. We did one a few years ago. Granted, this could happen almost anywhere, however it's not a surprise it happened there.
October is a good time to cruise and will have a lot less kids aboard. We've cruised on the Fantasy when it was out of Mobile. There is a couple reviews of the ship here on CruiseCrazies. Just click Plan & Research on the menu bar and you will find the reviews.