It would be interesting to see why you think Bitcoin (or other cryptocurrencies) will surpass traditional methods of payment (Cards, Bank transfers, payment gateways etc.).
why does it matter?
bitcoin was never created to "surpass" or replace anything. it is an alternate option that works in an entirely different way (in short decentralized) and the goal has always been to keep it that way not to compete with or replace anything.
Or if you think they have no future please share why.
that is an entirely different discussion which has nothing to do with your main subject. not replacing traditional methods doesn't mean complete failure and no future.
the rest of your arguments regarding 51% attack, speed,... are already discussed in dozens of other topics.
I think we have this misconception that Bitcoin can only be really worthy if soon it can be able to topple all the banks we have around. I am not so sure but I am not buying that crap...and we should stop that kind of non-sense because yes in the first place Bitcoin is not made for that type of thing. Why should a decentralized platform be compared to what banks which are centralized infrastructures can be providing. Bitcoin can stand on its own. Maybe we are just carried away from our philosophical ambitions that we have forgotten the big realities out there. Personally, I don't believe that big banks will magically cooperate with each other and then just suddenly decide that they will pour millions just to defeat Bitcoin. This is just another conspiracy theory to me. If I am a banker right now, I will not be threatened at all with Bitcoin because it is not making even a small dent with my revenues in remittances and other banking services. According to what I read, not more than 10% of the USA population is into Bitcoin and that means we still have a lot of years to work on to make it really go into mainstream.