Hi David Kristol,
Thank you for posting to the Community. Hopefully the answers I have for you will satisfy your questions.
Q: Is there an alternative to buying a new iPad and new version of the SlingPlayer app?
A: Yes and no. If you purchase a new iPad, you can log into the iTunes account and download the SlingPlayer app to the new iPad without having to purchase it again. However, it will automatically update to the latest version of the SlingPlayer app.
So, if you purchase a new iPad and download the SlingPlayer app from your iTunes account, you will be able to use the Slingbox with the Roku 3, however it will have to be the latest version and you will not be able to use the version that you currently have on the old iPad, besides on the old iPad.
Hope this helps,
Sling Media Moderation Team