there were definitely rumors of exactly that at the start of this season, but I haven't heard a peep in months. Word seems to be the season 4 will be the last one for Rebels before they start the new series, whatever it may end up being, so I would imagine they are planning some good storylines for next season, including what you mentioned.
OK so then my question is, what hints were there in TFA that indicated OB1? They were strong enough that daisy was surprised people didn't know.
She would have to be Obi-wan's granddaughter or niece or something. Lothal Calendar makes much more sense than After Battle of Yavin:
Episode 4 - 3277 (0 ABY)
Episode 5 - 3280 (3 ABY)
Episode 6 - 3281 (4 ABY)
Episode 7 - 3311 (34 ABY)
Rey was born in 3292 (15 ABY).
Her being his granddaughter would be cool if only because that means there's more kenobi story to tell. But, the question was her parentage, wasn't it? And there's no way he ever met her, so why would she have recognized his voice?