For how long will one have to wait to see new Bitcoin asic miners get released into the market? Four years or more? I am curious because all the available Asic miners are already getting older and less profitable, how long does it takes for Asic companies to build the latest Bitcoin Asic miners with higher Hashrate?
A higher hashrate on its own means nothing, it's always a combination of price, efficiency, hashrate, and lifespan.
An example, Bitmain can overclock their S19 XP and get 20% more hashrate at the expense of both efficiency and lifespan, or, they could underclock it to gain more efficiency and lifespan at the expense of both price and hashrate, stuffing more chips to get a 500th miners is something they do in a few weeks if they want to, but they will end up with a huge miner that draws a lot of power and won't sell easily.
Looking at the history, I don't remember there has not been a single year where all large ASIC makers didn't bring in a new model to the market, also, in some years they made a few models, it all depends on the market condition.
With that said really, I don't know what is the purpose of your question when I read this part
I am curious because all the available Asic miners are already getting older and less profitable
This will always be the case, looking at the most efficient air-cooled miner in the market right now which is the M50s++, if you were to ignore the cost, that miner makes a ton of profit in comparison to the power it needs to run, but that won't be the case forever, difficulty will keep growing, they will make better gears in the future, just like how the old miners such as Antminer S9 or MicroBT M10 are now pretty useless despite being at most efficient gears at one point in time.
As a person who mines Bitcoin, you need to understand that there will be no point in the future where you can just buy X gear and expect it to stay profitable forever, you will always have to assume that at some point in the future, the miner will make less than what costs in energy, also, taking into account the lifespan of these miners one should always assume that those gears will either die or stop making a profit in a few years.
So your buying model must be realistic, makes exactly no sense to buy a mining gear that can't ROI in 2 years at current difficulty, because that will only get worse as time moves on, but as long as your ROI is reasonably short (6-12) months you can somehow safely be sure that you will hit ROI and make some more profit before that gear is either no longer profitable or functional.
This is a never-ending game, you need to keep chasing the market, increasing your hashrate, lowering your power consumption, mining as a business is far from easy.