Can someone please predict when it will become available?
According to https://www.taransworld.com/SoulForge/ there are 38 troops left in the current cycle. It has not appeared yet so it will be coming up some time in the next 10 weeks. No one can narrow it down more than that since it pulls randomly from the pool of troops remaining in the cycle.
To piggy-back off @Redi1 a bit: since there are 38 mythics left and 4 show up a week, it’s relatively easy to figure out the percent chance of getting what you want, at least:
Next week, 4/38 = 2/19 = ~11%
Then: 4/34 = 2/17 = ~12%
Etc…hits 100% when the fraction is 4/4, obviously (10 weeks)
You can run a similar calculation to figure out the odds of it not showing up, like what people do to figure out the odds for failing to get a mythic with a certain number of keys, but. Either works out to basically the same (reversed) answer.