If Bitcoin core development suddenly stopped right now it wouldn't be very future proof. Trading volumes are irrelevant from a scaling perspective, what matters is number of transactions per second (tps). Right now Bitcoin has a really low capacity, just 7tps, way below VISA for example.
However, progress is underway on creating the Lightning Network , which will enable billions of transactions per day. Just 11 days ago a major requirement of the Lightning network was merged into Bitcoin core, and things are moving fairly quickly in the right direction.
I doubt anything will replace Bitcoin, further crypto-currency advances will likely be built on top of it (like the Lightning Network and sidechains). Ethereum is looking incredibly promising (has been dubbed Bitcoin 2.0), but I think it will be used primarily as a blockchain programming framework instead of as an alternative currency.
Lightning will require entirely new wallets to be created for it, and those wallets will be very complicated. It's a multi-year project at most.
The reality is that Bitcoin will fall apart if too much load is placed on it, and it's getting closer to its (entirely arbitrary) 1mb scale ceiling too fast for comfort.
What they choose to set as the minimum amount of throughput for each node is ultimately dependent on the lowest common denominator in terms of bandwidth for every node on the network. With a truly distributed network like this, you need everyone on the same page.
This is a valid criticism of bitcoin IMO. For example, there was talk about forking the network in August because of disagreements about what was reasonable to expect for the network-- Internet in China is expensive.