The word out of Redlands is do not expect a public beta of ArcGIS Explorer in June (I’m sure that is not a surprise to anyone given how many days are left). There are no short terms plans as far as I can tell for a public beta to be released in July. ArcGIS 9.2 Beta sites will continue to get beta updates to AGX so development will continue. I also believe there are plans to open the ArcGIS 9.2 beta to more people so you might be getting a copy of AGX that way.
I’m not really disappointed at hearing this. Beta sites still haven’t gotten ArcGIS Server (AGS) 9.2 Beta 2 so I’m sure there will be quite a bit of back and forth when sites begin to test AGX and AGS together. ArcGIS Explorer without AGS is only half the story so getting AGX and AGS right is very important.