Parts of it (the neighborhoods close to the beach, public transit etc.) may well end up being among the most attractive. Most neighborhoods will, however, probably remain poor and neglected for decades to come.
The dissonance will probably never get quite as bad as that between The White City and Neve Shaanan in Tel Aviv five-ten years ago, just don't expect all of Bat Yam to undergo gentrification and renewal overnight. In fact, I am pretty sure that certain neighborhoods will see an influx of haredim (ultra orthodox Jews), as Bnei Brak will be easily accessible by light rail.
The influx of new residents (be they hipsters, arabs, olim, nouveau riche, or haredim) may well exacerbate frictions, causing renewal to slow down. There is plenty of friction in Bat Yam as it is.
Damn. In a decade Bat Yam will be one of Tel Aviv’s best suburbs (or neighborhoods?) with the great towers, light rail and other public transport connections, the beach.