What is a concern is competition. I think there is a 50% chance that Bitcoin is replaced within a year with a higher valuation currency. Bitcoin is currently one alt-bubble away from being lapped... once that happens chaos will ensue because there will be just too many choices competing for crytpo dollars.
I think that's very possible but it would also highlight the absurdity of the alt market and market cap.
Say the Poloniex maniacs sunk their teeth into Wankcoin. Let's also assume someone held 95% of it and wasn't letting go. Wankcoin gets a market cap of $15 billion within a few weeks.
The Bitcoin killer has arrived. Except there's no GUI wallet. No lightweight wallet. No mobile wallet. No paper wallet. No ETN. No GBTC. No localbitcoins. No more than a handful of exchanges. No payment processor. No way to buy it with a debit card or bank transfer.
No one's battle tested it as all transactions are purely to the exchange wallet and once it's in there it never leaves. No one's bothered to look into how it's going to scale. Why bother? We're getting RICH. Someone holds 95%? STOP FUDDING.
In theory infrastructure could be easily swapped over. So industry hops on the bandwagon, says they never liked that Bitcoin shit anyway so ner and starts the migration. In the meantime the 95% holder does what any good alt market does and rapes it or a glaring technical fault emerges.
Suddenly Bitcoin has lost its sheen and Wankcoin has made everyone look like an utter prick off the back of one giant pump. To the outside world it's just proven exactly what those who were paying attention initially thought. It's amateur hour based on infinitely replicable code