I believe the use of ebony and rosewood as fretboard material has alternated in the years since the TBird was reintroduced in 1987 without too much thought given to it. Probably has more to do with what fretboard wood they have overstocked at any given period. From a visual aspect, I prefer rosewood and from an aural one probably too. The big plus of ebony is durability, but with my herd that doesn't really count. I don't think I'll ever wear frets, much less the fretboard on one of my basses down.
Going back to the TBird. With the reissue having stayed the same since 1987 with only minor changes as regards fins, pup output and fretboard material, the whole line is getting a bit long in the tooth by now. About time, gibson came up with something nre while retaining the essence. Sigh, I know what you chrome imbeciles are now thinking ...