How can I forecast the date Bitcoin will hit a certain blockheight? How can I forecast the date Bitcoin will hit a certain blockheight?

Are estimates for future halving and other important blockheights just based on the current height plus 1 for each 10 minute period between not and that date/time?

Are there any better formulas that also that take into account difficulty changes just after block halving or release of a new powerwide ASICs mining chips?
Take the difference (in days) between the current date and the date you are trying to estimate the block height for.

Then multiple that difference by 24 hours and by 6 (6 blocks per hour)

Current block height + (difference in days) (144) = new estimated block height

Difficulty changes upon release of new ASICs or halving are temporary (average block time will eventually revert to 10 minutes) and hard to predict. Therefore they cannot be accurately modeled in any equation.