Eh, the wording is a little different:When Luigi was revealed he came with a note that was something like "In previous games we've never revealed unlockable characters before release, but for the Year of Luigi we can make an exception", which says to me that at least Luigi, if nobody else, is an unlockable that they've revealed ahead of time.
We don't know with anyone else. It would be highly odd to have Marth and Lucina both be starters considering she's a clone of him.
A REAL pic of the day--Luigi joins the battle! In prior games, we've never introduced Luigi before release, but why not? This is the 'Year of Luigi,' after all.
I think your interpretation sounds most likely from that, but it could also make sense to interpret it as "Luigi's no longer a secret character."