which manufacturer will respect its delays, and that my friend is clearly impossible to predict.
Actually it's possible since there are some manufacturers that indeed honor their words. The hard part is to predict difficulaty and what it seems even more difficult is to see the obvious. That buying those miners don't worth it.
As far as i am concern, I have not heard from any manufacturer that sent on-schedule preordered products. There is always some delay of any sorts as it is frequent in such technological field. Thats why they keep it so vague when it comes to predict a release/delivery date ("end of june", "early Q2", "march"...blablabla).
Again i really think taking manufacturers word about the release of a product that is not even fully developed and tested is purely speculative and should be considered with extreme caution.
what makes worth mining is whether you are able to limit the unknown regarding the difficulty at some point.. AND the probability of you getting delivered by the estimated time of such difficulty. good luck.