You do know that the iPhone app will run on the iPad, it just does not have the better resolution that the iPad offers.
If you need it now, since you already bough the iPhone app, access the app store and as long as you use the same itunes ID, you can download the iphone app on your iPad and use it just like the iphone. Just make sure you use the same itunes account that you use on your iphone, When you use the same account, you will get a message validating that you want to purchase this app. say "yes" and then you will get another message saying you have already purchased the app and ask if you want to install again, say "yes". The other option is to connect your ipad to the computer open itunes and select your iPad, then the Applications tab and select the Slingplayer app from the list and sync.
Hopefully you will not have to buy the upgrade when it comes out.
At least you can start using it now.
The iPhone version is hardly a solution let alone even an option. The quality is THAT bad at 2x, especially if you aren't on Wifi. I was really hoping it would at least be out by the startup of the NBA season. No go. I have a couple places I go that love it when I bring in my iPad to watch movies and games. Unfortunately the quality of everything else is outstanding and when I try to watch Slingbox remotely on my iPad its just sad. Hope they get it out soon. I'm about ready to start looking at other solutions at this point.
Now that we finally have the iPad app and I have had time to use it, as good as it may be, it is only as good as your wireless connection. I have a Sprint Overdrive hot spot 3G\4G. Even in places where my hot spot indicates a 4G connection, it is too slow for what I wanted the app, to watch sporting events. This is not a fault of the app or Slingbox. I have a Speed Test app on my iPad and even at a 4G connection, I typically get a .5 MB download speed, which s too slow for anything. On one passing play in a football game, it buffers 3 or 4 times. I would appreciate knowing if you have had luck with other carriers.