(A big question is also if big talent Konjuh will be ready then ???)
I seriously doubt she'll commit to it this time. Don't see her on any onf the entry lists for 2019 so far, so it looks like she's missing the entire Aussie swing, and is probably targeting Doha/Dubai for February return. So I'd say it would be too soon to expect her back in the team.
Yes, until we know the nominations we don't really know anything. I'd like to see the strongest team possible, but with both Donna and Petra around their best ever rankings ATM, something tells me their focus will be on their personal achivements this time around.
Fett could've been a nice addition to the team, had her 2018 not taken such a horrible course.