Bitcoin bulls have a lot of reasons to be optimistic right now. Find out what could drive Bitcoin over the $1 million mark — and what might hold it back.Even if you factor in the recent wobble, Bitcoin (BTC -2.65%) has been on a tear recently. It’s gained almost 55% in the past six months, setting new all-time highs as quickly as Michael Phelps in an Olympic swimming pool. Over the past decade, it has outperformed many other asset classes.For some crypto bulls, the question is not whether Bitcoin will succeed but how high the top coin might go. ARK Invest’s bull case sees Bitcoin at almost $1.5 million by 2030. MicroStrategy (MSTR 0.65%) chair Michael Saylor goes even further: He thinks BTC’s price will reach $13 million by 2045.If you’re worried that you’re late to the Bitcoin party, those targets from big names are reassuring. However, they are also extremely ambitious — and I speak as someone who’s optimistic about Bitcoin. Let’s take a look at why it could happen. Then, I’ll explain why it’s unlikely.The case for Bitcoin to reach $1 millionAt its simplest level, for Bitcoin to continue to soar for the coming decade, people must use it. ARK Invest identifies several potential growth areas, including more countries adopting it as legal tender. El Salvador and the Central African Republic have already done so.Bitcoin could also take a serious chunk out of the global remittance industry, making it cheaper and easier to move money internationally. Straits Research valued the global digital remittance market at almost $23 billion in 2023, and ARK’s most optimistic predictions say Bitcoin could take 25% of that market.Bitcoin’s potential as a form of digital gold is another reason for optimism, particularly combined with increased institutional adoption. Like gold, Bitcoin isn’t controlled by any government. And only a fixed number of Bitcoins will ever be produced. That could make it a good hedge against inflation, though it still must prove itself here.Right now, optimism about the impact of a more positive regulatory environment has played a major part in the recent rally. But it is too early to say how this will play out in the longer term. Regulation can be a fickle beast.Here’s why Bitcoin’s unlikely to reach $1 million before 2035Bitcoin’s been hovering around the $100,000 mark for the past couple of months. As such, it would have to grow tenfold in the next decade to reach $1 million. That’s a lot. Especially for a relatively new asset that’s already proven pretty volatile and has a questionable environmental record.The approval of Bitcoin exchange-traded funds (ETFs) has made it easier than ever for investors to add the grandaddy of cryptos to their portfolios. That influx of retail and institutional money has somewhat lessened Bitcoin’s volatility and improved its reputation. All the same, people who own Bitcoin through an ETF aren’t actually using it to make transactions.If they did, they’d know this emerging technology still struggles