> But also to be fair, even though you give people N releases with both
> features available to do the conversion, there are going to be some
> significant number of users that simply won't do the conversion until they
> are forced to, even though they had 3 releases in which they could have done
> it.
Having overlap for at least one revision allows seamless in-place upgrade. Having zero does not.
No Dan, it does not allow a seamless in-place upgrade, unless you only ever upgrade once.
If SA version N+1 supports commands from N, and your config file is in version N syntax, you can upgrade seamlessly, but as soon as N+2 comes out, you won't be able to upgrade seamlessly anymore. If you're at N+1's syntax, you can upgrade to N+2, but as soon as N+3 comes out, you've got to edit.. And so on.
Unless there's some additional detail I'm missing, like an expectation that SA will actually fix your config files for you, I don't see how this offers seamless upgrades except in the short term.
