I rock a Blackberry, and according to the CrackBerry forums, these statements are not really true. BB stopped support years ago for my particular OS, and all that is happening on the 4th is EOL. Phones in the wild will / should continue to function as dumb phones. Confusing this issue is some BBOS's that only run on 2G/3G, and the announcement that 3G is ending in the US. Then again my BB10 is 4G, so this would seem to depend on which OS you have. Of course, in countries with 3G still, even this is not an issue.
Bottom line, at least for me there should be no change in functionality.