I'm hoping someone more knowledgeable
    about bitcoin can comment

I did and was quickly voted to the bottom.

    bitcoin can be competitive with
    centralized competitors like credit cards

In it's current form it can't. It's already running at max capacity. No further increase in transactions per day is possible.

If there will be a cryptocurrency that can handle as many transactions as Visa, it will be something else then what we currently call Bitcoin.

Lightning network allows trustless instant and low fee payments. It is at the embrional stage yet, and the whole structure has yet to be defined, but the point to point protocol for trustless off-chain instant transactions is ready.

Iota?

Correct. Glad someone has heard of it at least on hacker news.

So, the block reward is indeed increasing, but two other things are increasing very fast. First is the price per Bitcoin, and second is the number of fees per block. Just the day before yesterday miners received 1800 coins from mining and an additional 500 from fees. That's already over 20% of the total daily reward. This two things are more than compensating the loss of block rewards (in BTC terms). Things aren't expected to improve based on this.

It's kind of insane if you compare to other payment services (if that's how you use BTC). Not only do you pay $5-$10 per transactions, but that transaction also consumes 20,000-30,000 times more energy.

Well, transaction costs are already super high. I made a transaction yesterday for $5 and it was single input/output. But it was urgent, so I paid generously.

As the network grows, the demand for transaction grows too. The fees will not increase because the reward decreases. Simply miners will stop mining as it is no longer profitable. But this will happen in 2090-2140. So it is very far.

I think in the future, lightning networks and centralized wallets will be the way to go. The blockchain will be used by only a few big guys and transaction costs will be over $100/tx.

Well... Right now we have blocksize limited to 1 mb. If we will remove this limit and Bitcoin becomes a global currency, we can earn a lot from transaction fees. nChain estimates about 0.05 for a transaction if it will became us big as VISA. If you interested where is one youtube video talking about possible fees.