Getty Images; Chelsea Jia Feng/BIBitcoin is up 57% this year, and market players see further gains ahead.Investors are bullish on the election, as well as further growth for bitcoin ETFs. They also acknowledge bearish factors like regulatory uncertainty and a lack of a post-election narrative.It's been a momentous year for bitcoin, with big price gains to match some of the most important developments for the token in years.It started with the Securities and Exchange Commission's groundbreaking approval of spot bitcoin exchange-traded funds in January.That made it easier for average investors to buy and trade the crypto, and helped mainstream the token via fund offerings from asset management titans like BlackRock and Fidelity.In April, bitcoin underwent its scheduled "halving," reducing the amount of tokens miners are rewarded by half.