Maaaaybe another x3 on top of this x3? That could be possible and not unlikely but that is about the all they could do honestly. Which is why I highly think that the best course of action would be to expect a good deal of increase from ETH but not "substantial" as in what usually call a x10 or more would be about because that is unlikely for ETH right now.
Well Eth2 is supposed to scale Ethereum by about 3000x once the upgrade is complete in the next two years, which will obviously allow a vastly larger network of applications to run on Ethereum. We should see DeFi have the opportunity to explode on Eth2.
It also allows staking of coins, which is going to entice a lot of people to stake their coins long term and just pick up that income yield, and it will likely entice new big money players to buy enough Ethereum in order to stake to get that income. If let's say 30 million Ether are eventually staked, they would have an annual staking reward of 3.3%, which is a good yield compared to stock dividends, but add in the fact that your yield is being paid in Ethereum which is an exploding asset instead of cash or stocks that average about 7% annual gains over the long term, and Ethereum is a much more attractive asset to derive a yield from than the stock market. Already 1.29% of the entire supply of Ethereum is staked and the staking chain just started two weeks ago!
So yes between the increase in usage implied by a 3000x improvement in scalability and how much Ethereum is likely to be taken off the market to be staked, substantial growth in price due to Eth2 seems likely.