This is better than yours (the way you written the questions).

1. Unknown (maybe yes, maybe no) but I prefer altcoins will never reach or equal with bitcoin in term of; price and trust from people.
2. Unknown (we don't know what will happen in the future) if refers to my first point, it will take forever.
3. Adoption, acceptance, spread widely in worldwide (bitcoin and ethereum has these points)
4. The most significant thing is; bitcoin is the first cryptocurrency and altcoins just other copied, following bitcoin path.
There are a lot of altcoins which is better than bitcoin such as lower fees or faster confirmation time, etc. But, altcoins still can't reach bitcoin due to that (4th) reason.