Yes. I think vacations are something most people feel they have earned and they will still do it. Even if it means cutting somewhere else. However; some people may not be able to do as many each year though.
The cruise lines are looking at the drivable embarkation ports and improving facilities. There are about 30 drivable ports. Virtually ever American is within a driving port. Some are only seasonal right now. I wouldn't be surprised in the future to see Norfolk be a year round port. Next year Carnival is basing a ship out of Baltimore year round.
Even with higher airfare Europe has gained in popularity for cruises. The Euro exchange is poor, but with a cruise you have everything paid in US dollars.
At least 24 more ships are on order or being built, and set to debut between now and 2012.
Only about 16% of Americans have cruised. That leaves a large market for the cruise lines to tap into. Cruising has a high repeater factor.
I don't expect cruising to slow down at all.