If your source of energy gets cheaper, you would capitalise on that by increasing your hash rate in order to get an advantage in the hash checksum lottery. The profitability of bitcoin mining has always been your hashrate/cost, and your cost has always been the total cost of ownership of your equipment. That includes power.
Speculation would be fine if it helped price discovery but it has become clear to me that bitcoin is far too irrational for me to partake in other than keeping the little exposure that I've had so far. I'm sure there is some mathematical hash algorithm/proof of stake/distributed accounting that could serve a better job as a financial tool than relying on government-issued currency with a high risk of inflation as a result of poor debt management. But no crypto can satisfy all factors that investors would like.
* Decrease in transaction costs as the new protocol matures
This is historically what happened as technology, computing power, bandwidth improved. Bitcoin would require changes in protocol in order to make this happen, like Ethereum did.
* significantly better balance between early investors and late investors. A million increase in value between early and late investors just destroys the store of value idea as its a pure speculation instrument. A currency with a very stable inflation rate could outperform the dollar if enough markets used it.
* better integration with long-standing agreements like insurance against theft, loss, recalls and other tools everyone expects to be able to use from a functioning society.