i guess its will be dash , bitcoin cash , ripple
I do not think Bitsler will ad bitcoin cash, as long as I know Bitsler does not support any HF coin so I think the chance is very low to see bitcoin cash here. We know 2 coins that will be added already, 1 more coin which is still a secret but I like to guess it and I hope it wont be an expensive coin like dash. So maybe ripple, NEM or Stellar.
For me, any coins to be added will not be a problem. One thing for sure, with the many choices of payment methods applied, there will be many options for us to deal with transaction fees or confirmation times. I mean, when bitcoin or ethereum is so crowded, we have another choice to be picked.