Right now, everyone is creating sample/test code for the P2 and using the ".spin" extension. Except, these files are not compatible with Propeller 1. The new instruction set is not a superset of P1 spin, so existing P1 spin files aren't compatible with the P2 either. As a result, using ".spin" for P2 code is only going to cause increasing confusion. While working on the VSCode extension, I've been using ".p2asm" to distinguish between the two variations, but I'm not crazy about that. Maybe ".spin2" or something like that would be better.
If you have a preference for an extension (other than ".spin"), can we go ahead and switch to it now? If you don't have a preference, I suggest going with ".spin2".
(Edit: Chip has taken care of the filename extension in the V10 release, so I have updated the title to reflect the discussion topic that took over the thread...)