According to the Houston Chronicle, there will essentially be "no programming" for the first day, and the convention will be decided on a day-to-day basis.
From McCain:
I pledge that tomorrow night, and if necessary throughout our convention, we will act as Americans and not as Republicans, because America needs us now.
It seems as though Senator McCain is determined to turn this pending national tragedy into a political "show."
The plan is to try and get delegates and others involved with the convention to help in the relief effort, though I'm unsure what exactly they could do in St. Paul (it's assumed almost all the delegates are already there in Minnesota).
After cancellations from Bush, Cheney, Schwarzenegger, Jindal, Perry, it seemed that canceling the whole show was the next logical step.
No word how delegates will be addressed for the remainder of the convention:
As McCain prepared to be briefed about Gustav by officials in Mississippi, the Republican Party had no immediate official comment on how it will re-arrange the convention schedule, find substitute speakers or have Bush and Cheney address the delegates by video.
Per Tassojunior and the Houston Chronicle, the GOP should announce their new plans at a press conference at around 4 pm Eastern/3 pm Central.
On the Obama front:
In Ohio, Democratic presidential contender Barack Obama said he will mobilize some of his supporters to provide relief work and money to hurricane victims if needed.
"I think we can activate an e-mail list of a couple of million people who want to give back," he said, according to AP. Obama said he might visit storm-damaged areas when practical.
Clearly Obama understands that this has the potential to be a huge natural disaster, and it is imperative to do what's necessary regardless of the attention one might receive in the media for "helping." As has been noted, McCain cares more about photo-ops than national security and American safety because this is the 2nd time he has rushed to a disaster/potential disaster area (see Iowa floods) before he really should. He was even advised NOT to go to Iowa by their own governor, yet he went anyway.