I’d not worry to much about it if your not in a rush to get it and just order from Rightstuf. You can always call their 800 number and ask if they have a restock date. They usually can at least give you a estimated time of Arrival.
Off topic: I think the issue with Real Adventures of Johnny Quest part 2 is it’s one of Warners MOD DVD-r disc. There always seems to be one or two bad batches , then someone complains to Amazon and they get pulled for a little while or Warner waiting for enough orders to make a new batch leaving Amazon to relist with a new date. I honestly find Warners pricing on these to be more absurd then Japanese Anime pricing. I could see if the disc were standard disc but they are DVD-r type media. A more professional version of them mind you but still a DVD-r. I’m concerned with life of the media. If they were the more expensive kind they coat in similar to the stuff they use on Blu-ray I’d probably not be as concerned.