Honestly, the average consumer only saw that commercial, and it just said, iPad, April 3rd. No mention of reserves, pre-orders, etc. Just imagine someone you know who knows nothing about computers. Saw the ad. Goes to the store. Says I want an iPad. Will Apple inform them a different one is coming in a month? That is my question.
The average consumer is not going to reserve/pre-order it. They are just going to go to the Apple Store some point between April 3rd and when the 3G version launches.
That commercial will get people talking. Ordering will start on the 12th for both models, arrival times will be explained and there will be more talk. I'm certain the distinction will be very clear on physical order forms. Over the phone orders will generate receipts which will clearly differentiate. This is how any quality company would handle this. It's not worth it to have pissed off customers complaining that they would have waited or ordered differently had they only known.