I doubt Binance will be adding the Chinese coin GXShare (GXS) since it's virtually the same situationally as the coins they just delisted. If they play it safe and skip over GXS, SONM would be the fifth coin listed.
That is very possible. Also, binance did not say they will list the top 5, they only said they will list 5 coins
If this would happen than it will be a twist into this adventure now it deserve to be there. SONM has nice support from community all holders will love to trade this coin there. Otherwise we have to wait till next big release.