I hope XRP overtakes BTC but I think for it to happen in 2018 is a bit far fetched IMHO.
But then again, Adidas passed Nike and all it took was Kayne!
Lets not forget that Ripple went from $8B to $90B in ONE month. Bitcoin sits at $240B and is declining every single day.
I think it will happen very soon. Money is flowing in to Ripple in a extremely fast pace