In was recently reported that the number of unique Bitcoin addresses holding an excess of 0 bitcoins i.e more than zero bitcoin in them just got to an all time high
This shows an evident increase in the adoption of Bitcoin all over the world, although unique addresses does not necessarily translate to unique users of the network, it shows the growth of the network.
Is this evidence of Bitcoin going mainstream?
Would an ATH in addresses lead to a new ATH in the price?
This has little to do with adoption if anything. It might be that people are getting smarter and are using one address per transaction, as it was originally recommended by Satoshi.
As for the price, is has even less to do with it. Some online services like exchanges have also gotten smarter and provide users a new address every time they want to send funds to. While you can actually use the old addresses, the correct thing to do is use the new one for each transaction. So an active trader that is also moving funds into an exchange would also be using different ones. If they are smart, at the time of withdraw they would make sure to also use a different address, even when withdrawing from the same exchange.
Ideally, transactions and addresses would be the same number. Some people are lazy or simply don't mind, especially those that brute forced vanity addresses, maybe for donations or such.
In my country merchants very rarely take bitcoin directly, so you have to hit the exchange and sell them for the amount of the thing you want to actually buy that day. Tomorrow the price in fiat will be much higher so it only makes sense to exchange for the thing you want to buy that day only. This translates in several more transactions than, say, someone living in a country with a "solid" fiat, who can do only one large exchange for living expenses of the month (not the day) or so. And our transactions while more, are for much smaller amounts.
Price in my opinion will see an uptrend up or near the halving, then there could be a correction. But it might occur before the halving, it depends if the price moves too quickly or not. Maybe after halving (and possibly correcting, it it changed too much), price will stabilize some more towards its next 4 year march. Even if it might repeat some previous pattern, notice that the fluctuations gradually are less and less, this is the natural price maturing. It ill be even more clear after another decade.*
(*) Assuming your fiat doesn't collapse.
