I've actually been somewhat surprised by the lack of outcry concerning the impending demise of VBA. I wonder how much of it is because people are assuming exactly what you say, and that when push comes to shove, VBA will stick around.
If so, then it will have to be a complete port to 64-bit. You can currently use VBA in 64-bit Autocad, but it slows down the entire program quite a bit. I actually can't see many people being happy with that.
As far as VB, I suspect it will be around as long as .NET is around. I don't care for it myself, but in general, there seem to be quite a few more VB.NET programmers than C#.NET. As time goes on, things like Boo or IronPython might start to grab some market share, but a lot of programmers (especially the "weekend warrior" type of programmer) seem to like VB. And since all .NET languages get turned into CIL anyway, the particular language is not as relevant for .NET as it is in other circumstances.